The 49-mile Laugavegur is the longest hiking trail in Iceland, and it is also one of the most popular. Its well-worn tread, cozy huts, steady stream of trekkers, and frequent wood marking posts make it a relatively safe and logistically easy venture. And the scenery is top-notch: colorful rhyolite-containing mountains, hot springs and thermal vents, neon green mosses and grass, enormous ice caps, and raging glacier-fed rivers and broad gravel floodplains. If you only have enough time for a few days of backpacking in Iceland, do Laugavegur -- it's the best bang for your buck.
The northern terminus is Landmannalaugar (elev. 500m), which will remind you of a Himalayan base camp with its alpine look and its villages of mountaineering tents. It is 34 miles south to Porsmork, a peaceful valley that's about 20 miles upstream from the Ring Rd on F249. Some trekkers stop here, but I recommend hiking another 15 miles to Skogar, a small village on the Ring Road; the trail goes up and over a high pass between the glaciers Eyjafjallajokull and Myrdalsjokull.
If you plan to overnight on Laugavegur, you have three options: (1) stay in the huts, which cost about $40 per person per night; (2) camp outside of the huts in a designated camping area, which costs about $10 per person per night; or (3) camp in a non-designated area, which costs nothing. Not surprisingly I opted for the last approach -- I was equipped to camp outside in all conditions, and there were plenty of excellent campsites besides the designated ones. If you want to stay in a hut you'll need your own sleeping bag or sheets and you should make reservations, especially in the peak summer season.
It is recommended that you spend 5 days hiking Laugavegur but it is certainly possible to do in less. With a 40-lb pack (25 of those pounds were food) I hiked the entire trail in 28 hours, including an 8-hour overnight camp. After my Traverse, I ran and hiked from Porsmork to Landmannalaugar to Skogar (about 83 miles total) in 1.5 days. Laugavegur is not the easiest 49 miles I've seen, but it's far from the most difficult.
To reach Landmannalaugar you can take the Reykjavik Excursions bus (Route 11) from the BSI terminal in Reykjavik; it leaves at 8:30am and arrives at 12:30pm. If you are doing Iceland on the cheap, you can try to hitch. Landmannalaugar does not see much thru-traffic but it is a popular destination; you should be able to at least reach the town of Hella, which is on the Ring Rd and which is a stop on the Route 11 bus. There are several daily buses to Porsmork, also operated by Reykjavik Excursions. Skogar is on the Ring Road and you can either hitch or grab a bus from there. There is a bus schedule posted in the campground bathroom.
Below is a description of Laugavegur. The basic description is from the Icelandic Touring Association's website, and then I have inserted many of my own comments. http://www.fi.is/en/hiking-trails/
-- 12km, estimated walking time 4-5 hours, 470m net climb --
From the hut in Landmannalaugar (75-person capacity) the gentle trail goes through a rough lavafield "Laugahraun." It's a steady and often steep climb up the slopes of "Brennisteinsalda" and to a plateau. The view offers an incredible spectrum of colours, especially to the north. After 3 - 4 hours you arrive at "Stórihver," a hot spring and one of the fewe green spots visible in the first day. Early in the season the rest of the trail from here to the hut "Höskuldsskáli" is covered with snow; by mid-July 2008 it was mostly melted out. Chances of fog are very high so even though the trail is clearly marked you must be careful. More importantly, you can encounter cold and wet conditions here, so be prepared with good raingear and insulated garments. A walk to the icecaves (approx. 1.5km from the hut) is a must. The hut sleeps 36 persons.
The first part of the trail takes us through a vast expanse dissected by small ravines where snow lingers well into the summer. The trail cuts right across these ravines, resulting in many steep short climbs and descents; I recommend going cross-country about 400m to the east, which will keep you away from these unnecessary climbs and descents. If the visibility is good a walk up to the top of mountain "Háskerðingur" (1281 m) will reward your with a breathtaking view. Soon we leave the colourful rhyolite mountains and descend steeply into an area with dark palagonite mountains and glaciers. You will also notice a considerable increase in vegetation as you lose elevatino. The trail down the "Jökultungur" is rather steep but leads down to a friendly oasis on the banks of river "Grashagakvísl" a fine place to rest for a while. From there on the trail to the two huts by the lake "Álftavatn" is on flat land that can be marshy early in the season. There are two huts (58 persons, GPS 63°51.470 - 19°13.640).
-- 15 km, estimated walking time 6-7 hrs, 40 m net descent --
Just after the huts you should cross the lake's outlet (hopefully on a 2x6 plank) and follow the trail to the river "Bratthálskvísl". You could also follow the road here but you will still eventually have to ford the river, which even in early-August was impassable without getting your feet wet -- it is only shin-deep but it is about 15m wide. The trail takes us over the low ridge "Brattháls" into "Hvanngil" ravine. In "Hvanngil" are two huts, one built for sheepherders in 1963 and one for tourists, built in 1995. A short walk from the huts is the river "Kaldaklofskvísl" with a bridge for hikers. On the eastern bank of "Kaldaklofskvísl" the trail branches, one branch leading eastwards to "Mælifellssandur" (Road F210) but the other one southwards to "Emstrur" and we choose the latter. Less than 1 km from "Kaldaklofskvísl" the river you must wade "Blafjallakvisl," which in mid-July was clear, lower-thigh deep, and moving peacefully. Approximately 4 km further we come to the river "Nyrðri Emstruá," which is bridged. Soon we will be overlooking the huts in "Botnar" (40 persons, GPS 63°45.980 - 19°22.480). A fine walk in the evening is to the "Markarfljótsgljúfur" canyon.
-- 15 km, estimated walking time 6-7 hrs, 300m net descent --
First we have to go around the canyon of "Syðri - Emstruá" and there is a steep, sandy path down to the bridge. Then a walk through the area known as "Almenningar" with crossing of among other rivers "Þröngá," which is glacier-fed but which is widely braided at the crossing point and only knee-deep max. After crossing "Þröngá" a 40-minute walk up and over a low ridge takes us to the hut "Langidalur" in "Porsmork" (75 persons, GPS 63°40.960 - 19°30.890) Landscape and vegetation changes rapidly during this last section -- birchwood and all kinds of plants emerge, a welcome change after the desert now behind us.
-- 20 km, estimated walking time 7-9 hrs, 100m net descent (but a 900m climb to start) --
This is probably the most popular hiking trail in Iceland as it is relatively short but it can also be very dangerous because of sudden changes in weather that can occur in any season. It can be calm and fine on the lowland but as you climb up to 1000 meters you can get heavy winds, pitch-black fog or even snowstorm. From the hut at Skogar walk downstream to the bridge over the glacier-fed river. Walk due south until reaching the road, and then follow the road east up valley towards the hut Eystrihattur. Alternatively, you can follow the blue-tipped wooden posts across the gravel if you enjoy twisting your ankles. Once you cross the creek that flows from the canyon Strakagil, begin climbing steeply. The trail levels out briefly onto a rocky plateau before climbing steeply again to the pass "Fimmvorouhals," which early in the season will be snowbound. The pass lies between the glaciers "Eyjafjallajökull" and "Mýrdalsjökull." There is a hut above the pass, accessible by a 1-km long trail. Shortly beyond and slightly below this sidetrail is an emergency hut. Depending on the weather and your mood, either follow the wooden posts cross-country or follow the road downhill. When you get to the Skóga river, follow the river, not the road. This is an amazing canyon of endless green walls and fantastic waterfalls. You'll wind up right at Skógafoss, which is 60m high.