You want to set up a community about a subject you are passionate about.
How do you spend it? Do you pay for vB or IPB? Or go with something free like SMF? How do you advertise? What do you spend that $500 on?
For me, I'd get vB leased ($85), find a decent, sparingly used forum template ($20) and a domain ($10), then get some hosting for $5 a month.
So far, my 1-month expenses are at $120. This leaves me $320.
Next, I sit down for a couple hours and write a bunch of non-time-sensitive posts for a later date. Save these. Then, I would go to 2 different 'pay to post' places, and buy a small thing from each ($12+$12, $24). $50 I would allocate to banner ads on a couple sites.
Total now is $194.
$104 I would spend on PPC advertising with google and adbrite (I'd try intermissions).
Total at $300 even now.
For the final $200, $100 would go to products of that passion (if its websites, software. If it's coins, books maybe) to give away as prizes, and the other $100 would go to forum cash prizes.
How would you allocate?