The unions have a massive job on their hands to try and mitigate the damage the coalition is about to inflict on the UK. I suspect (if a couple of recent conversations with non-union types are anything to go by) that a fair number of people who haven't previously been sympathetic to unions will be showing an interest as the cuts start to bite. In terms of recruiting and organising people I wonder if any of the unions have taken a look at any of the stuff from social psychology and behavioural economics? A few random thoughts spring to mind:
1. Social proof is an important factor. People are more likely to join/become active if they think that others like them are doing the same. The suggests that union recruitment material ought to be as specific as possible - pictures & testimonials from people who work in that office/on that site will be more effective than general ones.
2. Loss aversion has a strong pull. As I blogged long ago, on one level unions have already understood this point, but it deserves re-emphasising. A lack of action/acceptance of the status quo presented as resulting in a guaranteed loss may make people more likely to take action.
3. Keep it optimistic. Like it or not (I do!) people are more likely to respond to an optimistic message than a pessimistic analysis. See Martin Seligman's work for details.
But as a very simple starting point I would recommend spending a few on this. It can't do any harm!