I just saw this in my inbox this morning and thought it was worth sharing:
http://m.athletics.mlb.com/tickets/info/ballpark-pass?partnerId=ed-11451146-989418633
Basically, you pay a one-time $5 fee and $20/mo, and you get a ticket to every single A's home game from June-September (not including playoffs). As far as I can tell, there's no catch. If you live in the Bay Area, seems like a no-brainer.
