1. Daily Indie Game – Indie game sales every day starting from $0.99. They have also some great bundles.
  2. Steam – Currently Steam is hosting the annual Summer Sale. Check out the awesome discounts (up to 95%)!
  3. Bundle Stars – Buy cheap games and activate them on Steam.
  4. Indie Game Stand – Dozens of games on sale every day.
  5. GOG.com – DRM-Free sales. Summer Sale started, so check out the great discounts.
  6. Humble Bundle – Probably the most popular one. Weekly game bundles starting from $1.
  7. IndieGala –┬áNew bundle every monday.
  8. Origin – Steam alternative from EA. They always have at least one game for free (about a year ago they offered Battlefield 3 for free).
  9. Games Republic – Subscribe to their newsletter for the latest game deals.
  10. Desura – Offering both DRM-Free and Steam games.