I recently found a place to purchase Mean Green (semi) locally. If you read pinrepair.com or follow RGP you've undoubtedly heard of this stuff. It's a liquid cleaner de-greaser that is immensely useful in pinball repair and restoration. It excels at removing yellow nicotine stains from pinball cabinets. I've also used it to clean old gummed-up grease from EM score reels (or really anywhere there's old grease), sticky flipper buttons (especially buttons you can completely disassemble - Gottlieb EMs, Sys 1, Sys 80, early Bally/Stern SS, etc.), stainless steel ball guides, unpainted coindoors, legs, lockdown bars, etc.
You can order it online from doitbest.com and have them ship it to your local Do It Best hardware store for free. I have mine sent to the store at 37th and Division and it takes about 5 days to show up.
http://doitbest.com/Multi-Purpose+and+A ... 646334.dib
Obviously, this is a liquid cleaner so don't spray it anywhere near your playfield, and remove any components from the machine before you clean them. It's pretty potent stuff, so definitely do a test spot before you go to town. It will take up paint if you leave it on too long!