This has come up for me recently, actually, and I finally decided just to find a group of people who (A) I already knew and liked OOC, (b) had RP that I could dig as well, and (c) I could use as a stepping-stone to rule New Eden!!!
Wait, maybe not that last bit1.
Anyway, I'm not sure that my current interests require much specifically out of a RP corp. That is, I like a corp that RPs because, hey, it's easier to pick up chicks that way2. But if you're focused on trade, industry, etc., then even a regular or RP lite corp can often fit the bill.
1: Or maybe so...
2: This may not be true.