Thought I'd share my primary sources for CE credit; feel free to comment and add yours!
(free!) ARUP Labs
(free!) Blood Bank Guy - selected podcasts qualify for CE credit through Wiley Health Learning. Listen to the podcast and take a 5-question quiz at WHL.
I also like paying for a year of LabCE in the year my certs are due. Currently this costs $95 for a year. I can finish up any credits I wasn't able to get for free, submit for renewal, then after my certs are renewed, I have the rest of the year to get a head start on the next 3 years.
Other sources I've been able to access free through an employer include Immucor and American Red Cross, but you need your lab's organization code to sign up.