If you just have small rust spots or "blooms", these can often be nicely taken care of. You need a very fine oil like baby oil or gun oil. This also is used in maintaining your putter's finish. Moisture is almost always the cause of finish degradation. Use a soft cloth rag or thick paper towel and use light pressure after applying oil to the rag or the putter. Small spots will often be removed leaving almost no mark. Wipe the putter down with a clean cloth and always keep it dry and in it's headcover.

You can send it to the Custom shop for restoration or have your local pro shop set up a refinishing.  The custom shop link is:

http://www.scottycameron.com/customization/modifications.asp?mp=1&st=customization