Last year I learned about, and picked up a few copies of the Sega CardGen MLB game cards. Actually, Kenny was my major source, though I found a couple team sets to use in trades.
This year's set has actually been "out" for quite some time, but I haven't seen any team sets or even affordable singles until now. Last weekend, I found a new box of 2013s for single-card sale. As before, cards have a while or black top and bottom border, with team colors used in the bottom banner. The number of stars on the card is an indication of the "strength" of that player in the game.
There are foil special cards available (I'll probably pick one up this weekend if I can get to a card store).
Kenny (and anyone interested in singles or team sets from this year) - I have yet to check Ikebukuro and Shinjuku but I didn't see team sets at my two expected sources yet. If you want individual players, I can get most of those at 50-150 yen each, and if you're willing to pay that kind of money (or offer up a really nice trade) I'll build a team set card by card. If you're willing to wait and take the chance later, I can see if team sets show up later in the year, as they did last year. (Foil cards were over 1000 yen each at my usual places, but might be cheaper at the other stores.)
I should mention to anyone who's been leaving comments or sending me emails - I am behind on emails and replies! One of my goals this weekend is to catch up on correspondence. If there's a trade or something in the works don't be afraid to follow up with another email though.