Another huge name in the industry, and another company that is willing to give you $5 just for signing up with them. Are you noticing a pattern here? Your opinion is WORTH REAL MONEY.
One neat little feature with Inbox Dollars is the option to play games and compete for rewards. It's not my thing, personally, but if you're into that, go for it. Otherwise, they have cash back programs similar to Swagbucks (plus surveys and all the other basics, of course).