Wiki software. (the current page/site is a running example), Info.
Own rating: ★★★
locatabl.com
Sites where people can appear on a map in different roles. Info. Running example: taxi.locatabl.com.
Own rating: ★★★
syncAMeeting
Site for synchronizing / scheduling of a meeting (without requiring large user commitments (only the one who sets up the meeting needs a Facebook account)). Info. Link to site.
Own rating: ★★
nsVote
non-secret-Voteing tool, using universal (OAuth) IDs like Facebook. Info.