Here's a map of their stations: http://www.dalgs.com/map9.htm
I worked for DGS at IAD
a few years ago as a summer job between years at school. Starting pay was $9/hour, and we had free pass privileges on Delta (upgrade to first class) domestically, I'm not sure what it was internationally. They served the United Express, Delta, America West, and Continental operations, and Northwest Airlink pushbacks. I was happily on the Delta side, which had the most mainline operations. Everyone was increasing their operations to fight Independence Air at the time, so we had hourly flights from Atlanta, among other things. One 757, one/two 737-800s, a lot of MD
-88s, and a lot of CRJs.
While I was there (2.5 months), they never got me a SIDA badge, probably to save on costs. Instead, I was out there every day, unauthorized, risking a few thousand dollars in fines. I made sure to tell MWAA (the airport authority) that when I moved on to work for them (Airport Operations).
The plan was for me to return and work for them that December. Unfortunately, because I didn't earn anything within a certain amount of time, I was automatically marked as inactive on their system, and would have had to start the entire hiring process again. They weren't ok with that, and wouldn't take me back on board, even though they had given me an "Outstanding Performance" certificate before leaving.
It was a fun experience for someone young, and I learned quite a bit about ground procedures that's useful to me in my current job (Northwest Flight Operations). I also got a lot of pride out of the work.