I've been doing e-rewards surveys sporadically for a couple of years. You earn e-rewards $s. Sometimes the surveys are interesting, mostly they're pretty boring. There are a variety of sponsors, including DL, CO, Borders, etc.

Redemption rates for Hilton:

$25 Level
1,000 Hilton HHonors® Bonus Points

$50 Level
2,500 Hilton HHonors® Bonus Points

$75 Level
4,500 Hilton HHonors® Bonus Points

$100 Level
7,000 Hilton HHonors® Bonus Points