A couple of union-related links.
First off, UnionsTogether (the trade unions affiliated to Labour) are running a campaign against the Tory plan to introduce tougher requirements for strike ballots - Cameron is reported to want turnout thresholds implying that a majority of people eligible to vote would have to vote yes - not just those people actually taking part in the ballot. This is obviously designed to make it more difficult to take industrial action. You can sign up here: http://www.unionstogether.org.uk/page/s/fightback
Also my own union Unite has launched a great site about the implications of the General Election for trade union members: http://www.unite4labour.org/ This site uses the Obama campaign model of trade unionists canvassing fellow trade unionists: if you are a Unite member and a Labour Party member or supporter as well you can log in and canvass fellow union members for Labour.