Here are some things that we have explored, established or simply stumbled upon which might be of interest to you.
'Livewires' in the urls refers to Room 3 - that's the name the class has given themselves.

Livewires Blog (Classblogmeister)

Livewires on del.icio.us - bookmarking site

Here is a set of short video clips on how to use some Web2.0 tools:
How to use del.icio.us
When you go to this del.icio.us explanation there are also videos on wikis, rss and social networks.
(Thanks to the Common Craft Show by Lee LeFever for making these easy to follow video clips)

This is a comprehensive site on a great variety of Web2.0 tools:
Educational Software wiki

Technospud - Jennifer Wagner in the USA runs a variety of international online projects for classes to participate in.
Some Room 3 students have participated in the 'SalutetoSeuss' project. You can see their powerpoint presentations by going to the Livewires wiki (click on the link above).
For more information about Technospud go to:
Technospud projects

This wiki by Alan Levine demonstrates 50 different ways to tell a digital story. The same story about a dog called Dominoe is told using 50 different Web2.0 tools with comments about each one.
http://cogdogroo.wikispaces.com/Dominoe+50+Ways

Here is an online mind mapping site that's easy to use. I played around with it for half an hour or so one evening and showed some of my students the next day. They picked it up really fast.
Mindomo mind mapping tool

Flickr - this video tutorial (18 mins) explains how to use Flickr, the online photo storage, organiser and sharing site.
Flickr video tutorial