Leahey.org

eHow and wikihow: Both exceedingly useful how-to websites, both for geeks and non-geeks. I find the wiki much more useful, and the subject matter is much more diversified, from health to relationships, finance to tech.
Makezine and Makezine/Blog: MAKE magazine is about the coolest magazine on the market. I highly recommend getting a real subscription, but the next best thing is definitely the blog. Updated daily, there are tons and tons of awesome how-tos and guides to be had.
Instructables: My personal favorite, Instructables.com took an awesome idea and produced an awesome how-to website. It makes posting how-to’s with pictures exceedingly easy, and more and more users are taking advantage.
CNet Howto: This is a mostly-tech howto and tip/trick website, but useful nonetheless. Good browseability.

delicious tagged howto: Del.icio.us is a repository for lots of useful information, and the subject of howto is no different. Tons of useful links, updated frequently (obviously).

Did I miss one? Comment it in below.