A thousand is just slightly better than nothing when it comes to promotional initiatives. Really, with that little bit of money, about the best you can do is take yourself out to a nice weekend somewhere and just continue doing what you're already doing in the way of promotion. A thousand bucks isn't going to give you anything that'll measure more than the memory of a few days of vacation.
The best way to promote your board is to be able to hire someone, part or full-time, who does this kind of thing for a living, or who wants to. Even a college kid might work. However you slice it, though, it'll take money, much more than a thousand. So if your site doesn't generate the revenue to make that worthwhile, you're stuck with gorilla tactics for which you don't really need money, except perhaps to pay an indigent tech worker in India or someplace like that to hack away for a few months at unscrupulous tactics to try to draw traffic your way. But even then, you're better off getting a naughty friend to partner up with you to do that kind of thing, since presumably the friend might, like you, be doing it for challenge or enjoyment. Some Indian tech dude isn't going to know enough about your site to know how to get the word out effectively. (He'll have that "50 posts for $5" mentality.)
Man, starting a forum today is really a bad idea. But old or new, it's all about traffic. It's just that with new, you're facing obstacles that I would wish only on a verified enemy.