Many times, when you crash, you'll get a lastexception.txt as well as the lastcrash.txt file. You can look at that file and maybe spot the problem mod name in it. Both files are hard to read though.
If one of the mods you use is MCCC, then look for a file named mc_lastexception.html and click on it. It will open in your browser. It is much easier to read than the game's lastexception.txt file. That might give you a clue to which mod might be causing your crashing. Not always, but a lot of the time, it will. And it will give you a list of all the mods and CC you have installed so you can look for duplicates so you can delete the extra files which can cause problems in some cases, especially if they are different versions.
Also take a look at what your mods do. Mods that do the same thing can conflict with each other causing problems so it's best to remove one or the other if you can't disable the duplicated feature in one or the other, so they don't work against each other causing problems.
Hope this helps.
