A very good Guardian opinion piece - Champions of the people - argues that unions are currently not very relevant, but as inequality increases they might become central to people's lives once again. There is also another Guardian summary, What is the state of the unions?, which says there is some optimism for British unions - union density is currently 19%, and in 2003 and 2005 this rose for the first time since the 1970s.
There is obviously some degree of re-energisation occuring in the New Zealand union movement - mainly in relation to unions serving those on low incomes. The Unite union is particularly impressive, and of course there is also a very important supermarket pay campaign, "Shelf Respect", in which workers have been locked out. For more info and ways to help, see: http://www.shelfrespect.org/ and the wikipedia report.