i've been working in clinical research for the past few years, and just got into medical school for the next year...
i've learned a LOT from working as a CRA (at three NY institutions, and 1 in chicago), but there's a ton of variability. some jobs are amazing, others will have you do little more than data entry.
IMHO, the best jobs are ones that are in small departments or in ones just
starting; when everyone else is learning the ropes too, you get more than
enough opportunities to get your hands dirty.
CRA jobs are hard to find, but mainly because people don't know where/how to look for them. i recommend going through your school's pre-health department, which should give some info.
outside of that, taking initiative is HUGE. find the departments at teaching hospitals you're interested in working in, and send the head honchos and doctors email directly asking for work. ask them to forward to people they
know that are looking for CRAs...
if you're looking to work for a company, it's easier to get a job at a hospital
in the above way first, then get some experience and move on from there.
as a stepping stone to med school, the job has been second to none. i've even ran into ex-applicants who gave up one they found other health-related career paths, either in hospitals or corporations.
-r