Software

I work on a contract basis in IT.
When a position is about to end, I submit my resume to online job sites. I get bombarded with phone calls/emails about potential opportunities. And quite often, a single opportunity is presented to me by multiple staffing agencies.

It gets hard to keep track of which positions I've been already submitted to, and which I/they did not pursue.

What process should i follow to keep track of where/whom my resume has been submitted to?
Should i ask for an internal requisition number for the positions?

I'm trying to avoid double submission, and save myself the time.