I got PMP certificate on 3/21/2009.
It will be expired on 3/20/2012!!
There is a requirement to renew it. I have to get 60 credits (so-called "PDU") by then. According to the provider's (PMI) website, there are a couple of choices to get the credits; Taking classes provided by PMI, classes in colleges or online classes. Practicing the project management knowledge, etc.
I also found the limitation that I can get up to 5 credits per year by practice.
Hmm, no choice to take some classes...
On-line one is reasonable. It may be good time to update and reorganize my knowledge, which is likely to be scrappy :P