Don't think there's a specific site for strum patterns for songs. BMFW some have the odd one or two but it's a bit hit and miss. If you have songs you're having problems with you can mention the song on here or maybe link to youtube and Members here may be able to help you out, seen a few members do that with good results so it's worth a try,
You don't stop laughing when you grow old; you grow old when you stop laughing.