Bigfish Games Collector's Editions (games with extra chapters & other extras) are usually $19.99 or $13.99 for their game club members. This weekend they are having a sale making any of them released prior to 8/1/11 available for $9.99 (or $6.99 for game club members). Also of note, collector edition games are worth 3 punches on the monthly punch card (free game for every six punches).
Here are the details as well as some recommended games.
Usually I don't think the collector's edition versions are worth the extra money (usually twice the cost), but this makes them much better values and there are some good games particularly if you like hidden object games.
Use Jayisgames or Gamezebo to get reviews, pictures or walkthroughs of games you find interesting.