1. g2play http://g2play.net/
DRM (Digital Rights Management): not applicable
Regional locks: no
Seperate shops (different currencies): yes, in a positive way.

This shop sells CD keys for games on Steam and other games. However, they're not regarded as licensed retailers (by VALVe) due to the fact that they do not ship the box itself, they just send you the keys on your mail. The prices are of course way lower than prices found on Steam. Left 4 Dead: 14.25 Euro, Orange Box: 11.26 Euro.

2. Good old Games http://www.gog.com/en/frontpage/
DRM: no
Regional locks: no
Separate shops (different currencies): no

Good old classic games for a low price. Duke Nukem is on sale here for 6 USD!

3. Direct 2 Drive http://www.direct2drive.com/
DRM: yes
Regional locks: yes
Separate shops (different currencies): no

Many different games, no separate shops. However, some games have regional locks, sadly those are the games that are most wanted (CoD:WaW, WH40K: DoW2 etc.).

4. Impulse http://www.impulsedriven.com/
DRM: yes
Regional locks: can't find any
Separate shops (different currencies): can't find any

Few games (sadly), however, it is worth a look.