here's a forum that might give you some ideas....
Free forum: support forum of Forumotion's users
i read this there:
Here is a list of some of the things you can do to promote your forum, some are free some are not.
1. Facebook/myspace/bebo etc. you and as many as your members whom can, add your site link to any of these that you have. Social networking sites tend to be very popular and you will find that you can add many people from forums similar to yours, to your face book/bebo etc. They may see your link and join your site. DOnt force it on them however and dont add them just for the sake of them seeing your URL they will soon work that out and it will give off the wrong impression
2. MSN - in the same manner add your link to your personal message on msn.
3. Free ads sites. There are a lot of sites out there (use google) that are classified ads sites. add a free ad to the section most suited to your forum.
4. If you see items on ebay or any other site like that add a link to the bottom of your item selling page.
5. Exchange links with as many sites as possible that are similar to yours. in google. if your forum is about music say....in google type add url music. You will probably find a lot of sites easily that will allow you to add your url to them.
6. You can use vistaprint (google it) to get 250 free business cards with postage needing paid only. Find shops that are connected to your sites theme and ask to leave some for customers. Send them to your members and ask them to pass them on. Leave theme where ever you can that will target the sort of people whom might be interested in your site.
7. if you drive or your members do, consider getting some car stickers made, that will go on the back window or bumper with your website address.
8. Make up a poster for your forum in paint shop pro or other graphics program, or ask someone whom has the software to do it for you, then paste it up on your site, so members can print it off and stick them up anywhere suited to your site.
9. Google ad words. if you can afford it some advertising on google may bring in more members. be careful though and research advertising with them well as it can be money down the drain if you do not get your keywords right. Facebook also offer advertising.