After investing a great deal of time and money in obtaining your PMP Certification, maintaining your credential can often slip out of your mind - until you realize that you've one year left in your cycle and 30 PDUs to earn! The usual track of taking third-party classes and seminars is an efficient way to earn certification hours (and according to PMI, there's no limit on the number of PDUs that you can earn this way), but if, like me, you are a freelancer or aren't reimbursed for educational expenses at work, can find this option far too costly.
In order to quilt together the number of PDUs I need cost-effectively, I decided to collect all of the "low-lying fruit" - 15 PDUs for performing project management at least 6 months of the year (category 2H) and the 15 PDUs for self-directed learning (category 2SDL), which you can garner by listening to Podcasts - I especially like Cornelius Fichtner's - or reading books, articles and journals. You'll be halfway to re-certification, essentially for free.
Depending on your talents and inclinations, the other thirty can be obtained through a combination of public speaking, writing, and volunteer work; see the PDU category limits at PMI's pages on Maintaining your Credential for more information.
I earned 5 PDUs for doing a presentation on "Procurement in State Government" at a monthly event sponsored by my local PMI Chapter. If you absolutely love to speak in public, this is a great solution. It's also a wonderful way to create networking opportunities, as you'll stay in attendees' minds as a resource for the topic which you've discussed.
Have you authored journal or magazine articles on Project Management, or are considering writing a book on the topic? Claim your PDUs; you can also receive credit if you co-author.
Finally, if you are a serial volunteer, consider the ways in which you can introduce project management concepts into your organization, and you'll be able to earn.. Do make certain to document your work and how the application of PM principles revolutionized their efforts, and have a person there who's willing to vouch for your work.
I didn't mention attending chapter meetings and volunteering for your chapter; although these are great options, I know personally that it's not always easy to get to meetings or find the time to add yet another volunteering opportunity to your schedule.
It is possible to earn enough PDUs for re-certification at close to zero cost. Often, your daily activities are already earning them, and all you have to do is just claim them.
How do you earn your PDUs frugally? Please share in the comments below and/or tweet them to @ehowepm on Twitter.