Yaaay. This time the sites that are GOOD for you.
Throwing out the most obvious first....
Steam - http://store.steampowered.com/
Steam, the fantastic digital download system everyone knows and loves. This is their official store. Great system. Great prices. Great deals. You can't go wrong.
GoG - http://www.gog.com/
Good old games! A good site to pick up old games such as Neverwinter Nights! Has plenty of games to choose from and like steam, has some good deals.
Greenmangaming - http://www.greenmangaming.com/
Another good site. Plentiful games which link up to steam, so make sure you have steam. Some really great deals seal the deal for a good purchasing site.
Getgamesgo - http://www.getgamesgo.com/
As usual. Good site, easy to use. Great deals.
- GLRPG bits: