Windows/Mac/Linux: Arora is a free, cross-platform web browser built on WebKit (the engine that powers Safari and Chrome) that we've mentioned once before, but its latest release includes some interesting new features by default, including built-in support for ad blocking.
Once you've installed Arora, switching on Ad Block is as simple as going to Tools > Ad Block an then ticking the Enable AdBlock checkbox. (It blocks ads using built-in subscription lists.)
Arora also boasts a similarly cool ClicktoFlash tool that disables embedded Flash by default until you click a Load Flash button — handy to have when you want to keep your browsing light and snappy (Tools > Options, then go to the Privacy tab and tick Use ClicktoFlash on Flash plugins). You can right-click any blocked flash to whitelist Flash from sites where you don't want to constantly click to allow, like YouTube, for example.
Apart from those novel features (both of which some people consider must-have extensions for browsers like Firefox), Arora has most of the basic features we've come to expect from a good browser, including history and bookmarks manager, private browsing, a download manager and all the rest. It's probably not going to make its way as your main browser just yet, but it's an interesting idea, and it's the first browser that we're aware of to incorporate ad blocking by simply ticking one checkbox.
Arora is a free, open-source download for Windows, Mac, and Linux.