WebFilter is a free Chrome extension designed to block access to objectionable or dangerous sites, including those that are pornographic, harbor malware, show drug use, or are heavy bandwidth users. It's a generally useful tool, although it is somewhat marred by its surprising inability to block at least one very obvious problematic site.
The free TrackMeNot Firefox add-on takes a unique and creative approach to protecting your privacy from search engines that can create profiles of you based on terms you search for. Rather than hiding your searches from them in some way, it takes the exact opposite tack: It inundates search engines with a blizzard of background searches from you, so that no practical profile can be built because there are too many random searches. It generates those search terms from a group of RSS feeds from sites including the New York Times, CNN, and others.
Coke or Pepsi? Kirk or Picard? Betty or Veronica? The great battles of the marketplace tend to be duels, and few people gripe if you leave out RC, Sisko, or Cheryl Blossom. The "Browser Wars" are no different, with "IE vs. Firefox" having replaced "Netscape vs. IE" long ago, and other options are often forgotten. Opera has been one of the strongest alternate browsers for a long time, and it was my browser of choice prior to Firefox. Opera 11 (free) continues the Opera tradition of doing something different instead of a minor reskin of someone else's codebase, and delivers a plethora of features that are actually designed to be usable, not to pad out a checklist.
Android phones are remarkable devices, and essentially are full-blown computers that fit in your hand. In lots of ways, they work well with your PC -- but not in all ways. One of the biggest issues is Android's handling of bookmarks and browser information. Your Android browser doesn't talk to your PC browser, and vice versa. If you find a Web page on your PC that you want to save as a bookmark, it won't be saved to your Android browser. Chrome to Phone is a nifty, free workaround.