I'm a fan of Paizo's Pathfinder RPG. This weekend I purchased PDFs of the core rulebook and the Bestiary. They offer an incredible amount of utility - I really like the internal document links. I am in the process of relaunching some old D&D campaigns and the PDFs have already proved their value.
I'm also exploring the Pathfinder Society program. I don't know if I will ever participate at an event or anything like that, but I already see some great ideas for my home games. The faction-based short scenarios are a great way to bring some internal conflict to an overall cooperative effort to the table, plus aid in player character development.
Time to work on some character conversion...