The writing center at my school is pretty good, but they lack the technical expertise needed to effectively edit scientific manuscripts. They do put on writing workshops every semester though, which are helpful. It may be worth finding out if your university does something similar.
I actually do manuscript editing specifically for grad students in the biomedical and life sciences. I'm not sure if this would fit your needs exactly, but feel free to check out my website if you are interested.
http://celestebrennecka.wix.com/perfectingpapers