We have approx. 3000+ rounds that was stored at our range in open containers.  We have done this years and recently(last 1-2 years) started getting mice in our range shack.  We noticed over the last year or so that our brass has turned a dark blue and appears to have been covered in a liquid???  The range is dry and no one has dumped anything on it so I'm assuming the mice have relieved themselves on our brass.  Is there anything I can do to clean and salvage the brass in order to send back to be reloaded or is it scrap?

Scrap it.

Although the amount is small, there is ammonia in urine. I wouldn't chance it.

I would call it scrap.

The blue is the copper leaching out of the brass from ammonia contact. Some of the brass might be salvageable but that depends on how much effort you want to put into it.

Even if you can't salvage it for use as its original caliber, there are lots of conversions you can do:
Any 9mm or 40sw brass can be salvaged to use as jackets for swaged JHP bullets, 303 British can be modified into .410 shotshells for the .410 SMLE conversions that were not reamed for US style .410 shells, 30-06 and 308 can be cut down into .45acp cases, etc.

Myself I like to fiddle with things and would try to save it, others here have less time than they do money and would scrap it, at the end of the day its up to you.

The cases will soon crack:

http://en.wikipedia.org/wiki/Season_cracking

Lots of guys STILL use Brasso in their media and have NO issues...

That's kinda what I was figuring I'd hear.  Thanks guys

Cat pee is worse. Ask me how I know.

At first glance I thought it said MOOSE urine.  That would have been much more interesting.

Just recently dug half a case out of the chamber of a 6mm remington because the owner used brasso. IIRC it was norma brand brass too, not cheap shit. he said it was only on its 5th or 6th loading. I didn't ask how long he tumbled or how much brasso he was using. I still have the case in the shop. It split right behind the neck. i'll have to RP a picture.

If brass gets any corrosion/blue/bluish-white crusty shit on it, CHUNK IT. it's not worth the risk.