I recently launched << url snipped to comply with forum policy >> been rather successful in drawing in members by offering 2 promotions.
The first is offering 1 month free banner advertising to the first 25 members to reach a post count of 30.
The second offer is 6 months free text link advertising to the top 3 posters once our community hit 100 registered members.
So far in about 4 days we're up to 15 members.
Anyone having trouble gaining membesr might want to try a promotion method similar to this! :D