Is there anything I can put on my forum to make a decent amount of money? - Whatever I put on the forum it must comply with google adsense TOS. - I don't want anything that requires users to sign up in order for me to make cash.( affiliate programs) Is there anything besides google adsense that I can put on the forum that will make me money by clicks/impressions? If not, any other ways I could make money? I have a very active forum and I want to make some good money.
Like what MTbiker said, you could add VIP membership and VIPs get exclusive access to some sections. If your forum is very active, you could try selling link space to other websites on the bottom. An easy way to get ads displayed is get a mod that will auto-reply to new threads with an ad.
You kind of answered your own question. If you want to make money off of impressions that's easy -- look for a CPM ad network. There are a plethora of them, but not all accept forums. Like the other posters said add a VIP usergroup or at least add a simple donate button/link. (you'd be surprised how many people are willing to support forums)
Be unique. Your members will be loyal and they'll support the site. Banner ads and google adsense is a deal breaker to your members. Especially if your promoting payed memberships simultaneously. JMHO
By the way how did you got that much posts? I have over 1200member's with only 220 posts. If possble please pm me.