This forum is full of reports, ideas, conjectures and reports on Google's advice for reversing Panda downgrades. I'd suggest using our Site Search [webmasterworld.com] to locate these threads - and there are a lot of them.
Some of the most detailed advice from Google can be found in this blog post from Amit Singhal [googlewebmastercentral.blogspot.com] - who along with Matt Cutts is spearheading the Panda "site quality" algorithm.
A Panda devaluation is not an easy situation to move away from. First, it doesn't seem to happen dynamically - but rather only at intervals when Panda is "re-run". Second, there are apparently many factors taken in combination, so what works for some sites might not have any effect at all for other sites.
Good luck to you. This kind of situation can take everything you've got and a looking at your websites in a way that may be quite new to you and your team.