Here's Mine:

A few years ago, had a business trip connecting on AA through Miami for San Jose, CR. In MIA, my three companions and I volunteered and recieved $750 CASH!(actually a check), a free RT ticket and an upgrade to Business Class on the next flight (4 hours or so later). We ended up taking a limo to Little Havana, having a Cuban sandwich and a drink, and thoroughly enjoyed our good fortune.

One thing - I have always recieved RT tickets in exchange for volunteering. Now, it's been a while since my last bump, but from the sound of this thread, it sounds like the airlines are leaning more towards the voucher than the freebie. What do y'all think?