I would definitively not run a contest unless you have a decent amount of users on your site, it would give a really bad impression to the new users to see a contest that has started and ended in that same time.
I would consider the webmaster related forums signatures, if you can't be patient to reach the amount of posts and place the signature by yourself, then just buy signatures from someone that is active on such forums and has a decent amount of posts.
If you have the money, then run a visible advertising campaign on webmaster related forums that would be your best way to drive traffic into your site, visible ad banner 468x60 size would be just perfect, text links (won't help much but few clicks it might bring).
If you see a website that has webmaster articles, comment their article and place your URL to link to your site from the comment.
Link to webmaster directories (there should be billions of web directories out there now days, even tho I personally don't like them, unless it's for a site that i want to get crawled and indexed).
Unless you have a decent traffic, don't give free things, don't run contests, it would be waste of time and give a really bad image to your forum.