Hi -I do fairly often and agree that current players are iffy (best time is spring training); minor league is usually pretty good (I got a Mike Trout last year), and retired are the best. Always send a nice note and a SASE and be prepared to not get back anything you send. A good site is sportscollectors.net and thebenchtrading.com has a TTM section as well. It is too bad they don't here.
Royals Super Collector; PC's of Paul Splittorff, George Brett, Mike Sweeney