Orc, Portware - tier 1, expensive, does just about every market known to mankind and I consider them to be the cat's ass. If you're going to bitch about the price of TT Pro, then don't even bother asking.
TT - tier 2, mostly futures, FIX supposed to work, I usually link spreadsheets to it and a MatLab link on Bloomberg. Very serviceable, I've used the product since '98 and was one of the original beta testers for the autospread and autotrader. I should have patented it and sued Harris. Ha.
GL Trade - tier 58, sux
Eccoware - was decent when I tried it several years ago, could do up to eight legs at once as I recall. Don't know where the product is now.
Goldman Sachs Algorithmic Platform - equities platform for their institutional customers; I want to try this one out, and hope to shortly