I really like Wikipedia. By allowing anyone to edit articles, it gives a certain insight into the workings of web communities. The community there does a great job at keeping pages from being (or remaining) defaced. I use it all the time as a quick reference for things. I’ve found it useful in the past when looking for some nice software to use. There are some articles that have listings of different software that can complete a task. Example: List of vector graphics editors.
Just for fun, check out Jane Barbe.