Many companies now are offering a "Get Paid To Surf" program where you get free money (usually $.50 to $.60 per hour) to display an advertising bar while you surf the internet. You want free money, right? Presumably, though, you want a lot more than the measley 50¢/hr that most companies offer. If you sign up for 10 different ones and run them at once, though, things are much more in your favour...alternatively, one can be run until it "maxes out", then the next, and so on (for you 18-hours-a-day junkies out there ;)

Money for Nothin' and your clicks for free

Adbar,  Referral Link	Version(s)	Pay & Max. Monthly Hours	Min. Payout	Window Geometry	WindowMode	Inactivity	Compatibility	Protection	AppType
AllAdvantage	1.2 ~ 1.3	$.50/hr 25 hrs/mo. Worldwide	$20	792x62 (Version 1.2)	Friendly	5 min.	+Utopiad +Cashsurfers	Screen Res. (No edit protect.!)	OCX MSIE 4+
Utopiad Cashbar	1.1	Percentage 25 hrs/mo. Pays you for any computer activity...	$20	650x63	Aggressive	~ 10 min.	+AllAdvantage +CashSurfers	CRC	Unknown (C++/Delphi) Uses free GoToWeb component
CashSurfers Cashbar Navigator	1.07	Percentage UNLIMITED Worldwide	$20 US $40 Foreign	788(+)x60 (Expands to fill the screen horizontally)	Aggressive Docks to bottom of screen only (no floating).	5 min. (?)	+AllAdvantage +Utopiad	Lucky Number dialogue each hour	Unknown MSIE 4+

These cryptic informations are described in more detail below...

Comments:

AllAdvantage bar is the "friendliest" of the bunch, with a fixed per-hour payout and a friendly windowstate. It keeps tabs on screen resolution, displaying an error message if the screen resolution is changed to below 800x600.
Version 1.2 exits when low screen res. is detected.

Utopiad has a unique inactivity detection: a "status bar" on the adbar counts down for about 10 minutes' worth of little blue bars. When the status bar runs out, the adbar stops counting your time until you run your mouse over it. Running the mouse over one of the ad-displays refills the status bar... unfortunately, if Windows can't see the bar (ahem, virtual desktoppers) this has no effect!

CashSurfers' Cashbar Navigator: The "Lucky Number" dialogue is a box that pops up once an hour for you to click on to indicate you're still active. Presumably, this foils some kind of cheating method (the "Lucky Number" is a somewhat meaningless, random # that appears in the windowtitle to discourage cheat-scripts(?)).

Cheating (why NOT to)
Yes, there are cheat programs available, Trix and MyAdvantage being among the first (I did my research ;). They range from automatic mouse-mover and button-presser scripts to actual emulators that don't show banners but only simulate the protocols used by the adbars. The programs exist, but for the sake of your account don't use them! Think the adbar companies aren't aware of these? Some have tried, some have gotten their accounts nuked within about 2 days after using an emulator. In addition, at least one adbar (Spedia) will actually report you to OTHER adbar companies! E.g. if you are running an AllAdvantage emulator with Spedia, it will tell AllAdvantage about this. Monitoring of other applications is somewhat "shady" and (to my knowledge) not disclosed in the privacy agreements (Spedia will definitely not appear on my list!), so be careful what you are running alongside your pay-to-surf bars, particularly warez searches or cracks (if you're into that sort of thing)....

Referring others to the adbar programs makes you even more money!!

All known adbar programs have a referral program by which you can make exponentially more money, by referring others (e.g. your friends) and having them mention you when they sign up. When they do, a portion of the advertising money the adbar company would've otherwise kept for itself is now redirected back to you! Then, when someone signs up under them, they get more cash just as you did, and you get still more for this and all other "extended referrals"--they will typically credit 3 to 5 levels of referrals, meaning that even when your friends' friends' friends' friends' friends sign up, you are credited with additional earnings. "Not only can you get paid when you surf, you can also get paid when your friends surf. And their friends. And THEIR friends." Sort of like a pyramid scheme, but perfectly legal.
For more information on how the referral systems work, see the FAQs on the companies' websites. They all work generally the same way, but some details (such as level of referrals, percentages, etc.) are different for every one. No matter which one it is, If you sign up a lot of people, you make a whole lot of money!!

Explanations:
 

Adbar & adbar name:	Name of adbar (company), application internal name (the program name as it appears to Windows).
Versions:	Range of versions that are currently operable (older versions are sometimes desirable to bypass new "features" in updated versions)
Payrate & MaxHours:	How much they pay (usually per hour) and how many hours you can rack up each month. Also, what countries these rates apply to. "Percentage" indicates a variable payrate based on a percentage of how much the adbar company receives from sponsors.
Min. Payout:	How much money you have to accumulate before you receive a cheque.
Window Geometry:	Size (width x height) of the adbar window. Smaller is better!
WindowMode:	The "aggressiveness" of the program's windowing scheme. In general, friendlier windowing assures more 'flexibility' for the user and better compatibility with other programs. Also, anything noteworthy about its windowing mechanisms.
Inactivity:	Program's inactivity timer; that is, how long before it stops counting.
Protection:	Things built into the programs to prevent cheating.
AppType:	Information such as what programming language the adbar is written in, any required components/dependencies, etc.

Criterion for listing on this page:
Program must be an adbar or similar, e.g. no paid-to-read-spam or paid-to-tap-dance-naked-in-Times-Square programs.
Adbar must already be released and paying (no Vapourware!)
Must support all major web browsers--No "You must use only our custom web browser" or "You must use Microsoft Idiot Exploiter" (some require IE components be installed, but damned if they're gonna make me use it!)
Adbar is available worldwide or in significant/major countries (no "For Estonia residents only!")
Referral programs don't "cheat" referrers--that is, users don't get paid any less if they were referred by another user vs. signing up out of the blue.
Adbar company follows an accurate and up-to-date Privacy Policy and will not disclose personally-identifying info.
And of course, to reduce the occurrence of nasty surprises, I am personally testing each of the adbar apps listed here....