I run a general forum called Xtreme iTalk which can be found here:
http://www.xtremeitalk.com
It's been up over a year and has a PR4. The domain itself is older than the forum has been up. It gets 700-1000 uniques a day generally and half a million hits a month. There are several hundred registered members, most of which are active. There are about 24 thousand posts so far, always increasing of course!
Your link would appear on every single page at the bottom right under the posts so it will be seen very often. I personally see that area thousands of times a day.
My prices are as follows:
1 Month Text Link: $8
1 Year Text Link: $40
1 Month Image Link: $15
1 Year Image Link: $80
As you can see there is a massive discount, (more than half off) if you buy a full year. I also am accepting amounts in between (so if you wanted 6 months of an image link I wouldn't charge you $90 I'd probably slap that down a lot since it's still a bulk amount)
Cheers!
Taylor