Wikis, weblogs, mashups, photosharing, mapping, social bookmarking. People who start to learn about web2.0 tools, ask me where they can get a good and short overview of the various web2.0 tools. Honestly, I don't have one great resource to recommend to them. It's quickly overwhelming for people new to the field. Seven pointers:
1. Euforic is developing a web2share wiki, which is good basic resource.
2. The commoncraft show with its series of videos on tools like blogging, wikis, social bookmarking, twitter. It explains the advantage of the tools in very clear easy to understand language.
3. Tim Davies has developed some one page guides like this on social bookmarking. You can access the whole series here.
One level up in terms of overwhelminess:
4. The top 100 social media blogged by Steve Dale
If I really want to browse for tools (level 5 in overwhelminess) I go to:
5. Go2web20 website or
6. The organizer's toolkrib (less elaborate) and
7. The Seomoz web2 awards website