Apple has an app called iCBET which is a collection of questions in many subject areas. The complete package costs about $10 but gives a lot of sample questions.
CABMET (Colorado Biomedical Association) offers a training/review class several times a year. They have a very high pass rate. Visit their website to learn more.
AAMI has a review CD.
CRES Certification /US
RSTI offers some review/study material.
CLES Certification /US
CCE Certification / US