Although in Wikipedia, you can find almost all kind of content that you are looking for, it's sometimes good to try new things. Here's a list of five websites like Wikipedia that you can also try.
1. Citizendium - http://en.citizendium.org
2. Wikinfo - http://wikinfo.org
3. Knowino - http://knowino.org
4. Everything2 - http://everything2.com
5. h2g2 - http://h2g2.com
These were alternatives to Wikipedia. There may be more websites than these but the ones mentioned above look similar and also offer similar kind of material that is on Wikiepdia. Do you use any of these websites, or any other? Would you like to recommend any such website? Share with others your recommendation in the comments section below.