I made this for myself (I've got the memory of a Goldfish) but I thought maybe someone else might find it useful. Its just the IT/MPTM effect list taken from the OpenMPT manual, I've removed anything for other formats (I only use MPTM format) just because I found all the commands for other formats confusing. Its as compact as I could get it and still be readable, but it still takes up 6 pages. PDF format.
I'm hoping I'm not stepping on any toes posting it, but I'm sure the 'OpenMPT mafia' will send the boys round for a chat about my knees if I am. (better add a LOL here I think)
OpenMPT_ Effect Reference.zip
Nice :)