Chromium runs GreaseMonkey user scripts, apparently. It also says here that “script edits are picked up [from the file system] automatically; just refresh the page to see the changes,” which is something that annoyed me with Firefox’s GM Addon — the files were buried, crazily named, and you had to use that janky addon manager bullshit to make/reload changes. What is that? A directory full of user scripts (now ~/.js on my system) is a perfectly simple setup. Combine that with right-now reloading and I might actually be able to develop these things when I need them.
Anyway, this AdSweep thing is what led me to investigate; looks pretty reliable if you can get through the GM setup.