Send Earnings and Inbox Dollars are set up almost identically. You sign up with them and they send you emails with advertisements in them. You hit the button at the bottom of the email confirming that you read the email and they credit your account. Now these are by no means big money makers. It took me about a year to make $30 with each of them. Some people would never even bother with such chump change - and that's totally fine. But for me, I don't mind clicking a few extra buttons a couple times a week and getting $30 extra dollars in my PayPal account at the end of the year. If you don't have a PayPal account, they will send you a check. I would also recommend setting up a "junk mail" account if you are wanting to do this sort of thing. That way your regular email address won't get overtaken with all of their emails. Both Send Earnings and Inbox Dollars are now offering a $5 sign up bonus.
Then there is Pinecone Research. I have tried tons of online money making surveys and this one is by far the best. So many survey sites make you take long annoying surveys for just a few points or pennies. I don't know about you, but my time is much more valuable than that. Pinecone on the other hand, pays you $3 for each completed survey. They also will give you the opportunity to try out new products. Our family has been able to try several up and coming products for free, give them our opinion and then get $3 for it. Pinecone isn't the easiest to get into, but they are accepting new applicants for a short period of time.
How about you? Have you tried any of these or anything like them?