During the summer school on Technology-Enhanced Learning Peter Kraker, who led the session on "Using Web 2.0 in your PhD", asked the question, what are your five Web 2.0 tools you are using for your research? Here are mine:

1. Google Scholar: Mostly I use it in combination with the Publish or Perish tool, which ranks the results as a hint of highly cited papers (although I am not a big fan of such metrics, but it helps). Sometimes I cross check with Microsoft Academic Search, which has additional information about authors, timelines, co-author graphs, etc.
2. To manage my bibliographic references I mostly use Zotero, a firefox plugin, which let me easily add metadata from publications to my repository as well as it shows me analytics of my publication store. It also does a good job in converting the publications in all forms of citations styles. It has also the facilities of sharing resources with other to build publication social networks. But the ladder one is less explored by myself.
3. Google docs and Etherpad for collaborative writing in combination with video conferencing tools like Skype or Flashmeeting.
4. Social Networking tools: I mostly use TELeurope, a social networking platform for people interested in Technology-Enhanced Learning. First I was thinking about using facebook or linkedin but discovered limitations regarding community building in the TEL area. TELeurope is thematically oriented on Technology-Enhanced Learning and provides for this purpose more tailored tools than the mentioned social networking platforms. This includes not only the group tools but also facilities of blogs, wiki-like pages, the liking of activities, podcast infrastructure, embedding of external widgets/gadgets, publication infrastructure, status updates (which can automatically be send to Twitter), to follow the activity of other people, a personalized dashboard and profile page, and some more. Another benefit is to have an aggregated view on all activities in the TEL area coming from all activities. This means that an activity can be visible by all TELeurope members (currently over 1000 real users), and not only by the group of the mentioned other social networking platforms. TELeurope is also set up in a way that updates are automatically shown in other services. This includes for example a TELeurope status update to Twitter features and TELeurope blog and wiki posts to a Facebook page. And more from a technical perspective. TELeurope uses the open source platform Elgg and therefore allows to engineer the platform for all upcoming needs of the community, compared to proprietary systems. And the developments made at TELeurope are made available to the open source community.
5. For publishing Workshop proceedings I use by now ceur-ws.org. Your proceedings are quickly online and are freely accessible. You can find an example of our Workshop about Research 2.0 at the EC-TEL 2010 conference here: CEUR-WS.org/Vol-675

You can also participate. Write down your five tools and tweet the link with the hashtag #jtelss11.