I really like the idea of howtoforge and if it wasn't for a bit of writers block, I'd contribute more. This idea I have is kind of related to the idea of howtoforge, but on a broader scale.
I ran across the site '43things.com' today and thought it was a decent idea. The only bad thing about it, I think, is the lack of community support. For instance, take Learn PHP
for example, the comments are just full of stuff like "I learned it" or "It's worth learning". Nothing to actually help the 298 people learn PHP.
So my idea is to create something where people could "enlist" in certain things they want to learn. That person, and other people, could add different resources, tips, books, webpages, whatever, that would help teach that topic.
I browse these forums once a week or so here and always see different topics where this could be useful. Take for instance the thread on SpamAssassin Rules. Someone could create that lesson and others could post different links and resources on how to write your own spamassassin rules.