I tried to figure this out on my own by checking the mod's pages and comments. I've tried disabling things but I can't figure it out. Can someone take a look at this screenshot of my active mods and tell me if any of them cause problems?
It could just be my system but the lag doesn't start as soon as I fire up Skyrim. It starts after maybe 30 minutes of playing. Alt+tabbing out of Skyrim and alt+ tabbing back into it fixes the lag temporarily. Also the game used to run fine and I cannot pinpoint when this lag started. It's not like I added a mod and suddenly things got laggy. It was fine, then suddenly it was laggy and I'm not sure how to fix it.
Only thing I haven't tried is vanilla Skyrim and readding mods one by one and testing them. I don't have the time or patients right now for that - just want to play the game.

http://img.photobucket.com/albums/v80/castrostaal/skyrimmodss.jpg