Monmouthshire - set up a blog for reading groups and events and promote using a RSS feed
NLW - set up an organisational blog
Cardiff University - social bookmarks for student reading lists, staff blog to improve staff communication
Coleg Llandrillo - looking at screencasting
RCT museums - Myspace for news
RCT - set up Facebook page or blog to promote the library service
UoG - Facebook for staff to promote team working

Other suggestions:
Raising awareness of Web 2.0 tools amongst (library) staff and working collaboratively
Integrate web 2.0 tools into library OPAC
Instant messaging reference service
Integrate news (RSS feeds) from other sites into Archives website