I agree that most of the spots are already taken. I know someone who made the switch this year. She interviewed around Sept and the spots were filled by November. There were 2 spots up for grabs with 100 applicants. I may be mistaken but I think these spots get filled earlier in the year and that most have been taken well before the Catagorical match.
You may want to get your application together and start contacting the programs for next year's spots. The program that she matched at would not consider interviewing her until she had notified her PD of her intentions. Also, she was required to have all LORs from her program because they would not accept any LOR from medical school.
CA-2 spots are typically quite difficult to come by, and why you're looking for one raises questions: Why are you leaving your current program after one year? Are you going to be good enough to join our program and not be behind our residents that have been training in our system for a year? Are you leaving/getting kicked out because you're a problem, etc.
If you really want to leave your program, you need to discuss that with your PD because most programs aren't going to talk to you unless you've got your program's blessing to go. Once you've got your program's blessing, then send a CV and cover letter to EVERY program director explaining your circumstances, why you're leaving your program, etc. Then just hope for the best.
If you're actually looking for a CA-1 (PGY-2) spot, then most are already gone, and most of the 2008 CA-1 spots are about to be filled through the mamtch, but the process is the same. Send a CV and cover letter to every program director, and reapply through the match this fall.
I would agree with the above thread that in general a current PD's knowlege/blessing is necessary before looking for another spot. That being said, when I was interviewing at Utah, I heard they might have an opening.... Don't know whether it's since been filled or what the exact story was.