I'm using stock 1.1RC3 ( no mods ) and I've just discovered something new since last week. You can put adsense code in the forum's description area. No mods, and SMF displayed the ad correctly. Just copy and paste the adsense code into the textarea box. I've tested with InvisionBoard forum's description too, but failed. The PHP code in IPB replaces newline to br tag. So, for those who wants try something new, you can use your creativity by adding ad in the forum's descriptions. You can view the sample at http://protoncars.biz
This only tested on SMF 1.1RC2 and 1.1RC3. Perhaps anyone can test it on other forum - SMF 1.1RC2 & 1.1RC3 ( tested and working perfectly ) - IPB ( Trial version not working, due to nl2br() function ) - VB ( not tested ) - phpBB ( not tested )