The Antec Quattro 850W would be at the top of my list of considerations. It's semi modular (some fixed cables, some removable) and a great quality unit at a very attractive price.
Ultra's X3 800W is another very good unit, but also significantly more expensive.
Seasonic's M12 700W is superb, but also very expensive for a 700W unit. Ditto for Enermax's semi-modular offerings in this range. The Infinity 720W is a very high quality unit, but with the high price and abnormal rail distribution issues I wouldn't really recommend it.
Silverstone's Decathlon series is good and reasonably priced, although 850W is pushing the platform a little, it still performs well. These days I'd avoid the Striders, though.
XClio's and Thermaltake's modular PSUs are solid platforms as well (actually the same platform, I believe). Good value, well performing PSUs.
Those would be the main ones I feel are worth considering. I'd pass over the OCZ/FSP/Kingwin/NZXT/Xion/Topower units at this size.
Do you have a budget in mind? What will it be powering?