The Alpine Journal – Publication of the oldest mountaineering club in the world. Full-text searchable (and freely available) from 1930 on!
Alpinist – One of the premier climbing magazines, released quarterly. The site also has a lot of current news and writing.
ExplorersWeb – Dispatches & news on mountaineering expeditions, among other things.
SummitPost.org – source for (user-submitted/curated) information, photographs & trip reports from around the globe.