MDMA mixes fairly well with most of the standard party drugs (imho) - MDMA + Ket, MDMA + LSD, MDMA + Shrooms, MDMA + Nitros
If your experienced with LSD then take half a dose and combine with MDMA, that way you know roughly how long your going to be tripping for and the strength of the trip etc.
These combos threads are normally frowned upon though as mixing drugs isnt really harm reduction!