Get the Cat A 7 PDU by viewing and gain knowledge from ProjectManagement.com (PMXPO 2013) before it's gone. It's free and is available through July 25th 2013.
There are many other activities out there we can do to be updated and relevant as a project management practitioner without costing a lot. Though not everything is free, maintaining the PMP credentials should not be all about spending excessive money (own or company's) but the passion and relevance in the project management professional.
This plus another yearly IIL’s International Project Management Day should take care of the bulk of yearly PMP PDU requirements estimated worth approximately $100 (USD5-10 per PDU). To fulfil the rests, there's nuggets (1-3 PDU each) from other various sources e.g. Twitter and of course activites we perform as project management professions in our daily life.