Okay, you're looking at browsers. Let me add in my two cents:
IE [http://windows.microsoft.com/en-us/internet-explorer/products/ie/home] - Sucks, if you're using IE5, IE6, IE7. It got a bit better in IE8, but was still questionable. With IE9 things are looking pretty decent, though, personally, I just don't like the look of it. I keep it around, mind, because IE has a different standard for webpages, and some are still stuck in the past and won't load on any browser but IE.
Firefox [http://www.mozilla.org/en-US/firefox/new/] - It's not bad, if you're using something like 2.0. It's been getting more and more bloated, though. I quite like it because it is open source, and there are some great extensions for it. I used it for, oh, probably ~8 years or so. On the other hand, I've noticed over the past year it just kept having increasingly higher load times, would crash more, and would often have memory leaks. So, I decided to switch.
Google Chrome [https://www.google.com/chrome] - I don't like the idea of letting Google onto your computer. That's just a personal thing. I also don't like the Google Toolbar that IE would automatically install. But, for the idea of Chrome itself, I like. Which brings me to...
Chromium [http://www.chromium.org/Home] - It's basically Google Chrome, but without the Google. It's open source, too, so it's open to the community. Also, if you're a big enough geek, you do have the source code, so you can compile it, if you wish.
Iron [http://www.srware.net/en/software_srware_iron.php] - It's based on Chromium, but has better privacy settings. A much better alternative to having Google on your computer; it is what I'm currently using [well, that and Firefox still... Firefox is still my default browser, but I prefer Fe]. However, some people tell me that it's impossible to compile it without errors, so for some, it's iffy.
RockMelt [http://www.rockmelt.com/] - Which you may see referenced, it is yet another Chromium-based browser, but this time it is more social-media oriented. For example, Facebook is integrated into the browser in notifications/chat, etc. You can also integrate Twitter feeds, RSS feeds into tabs in the browser. It is, however, still in beta, and I believe you may need an invite to be able to use it. It's definitely not for everyone, but for some, it's a dream come true.
Pale Moon [http://www.palemoon.org/redist.shtml] - It's based on Firefox, and is optimized for efficiency, though is only available for Windows. Most Firefox extensions are compatible with Pale Moon, and is still open source and freeware. I haven't used it and thus cannot say anything about performance, but if you're looking at Firefox and are using Windows, you might want to give it a shot.
I am not well-versed in Opera [http://www.opera.com/], SeaMonkey [http://www.seamonkey-project.org/], Maxthon [http://www.maxthon.com/] or Safari [http://www.apple.com/safari/], so I can't really say much on them, other than that they exist. And that you can get a portable version of Opera. [You can also get portable versions of Iron, Chrome, SeaMonkey, Maxthon and Firefox from portableapps.com [http://portableapps.com/apps]; for those computers you use that aren't yours to mess with, but so you can still use your favourite browser.]
In the end, there are many browsers to choose from [the ones I listed are the the biggest ones], and it's up to you to find the one that's right for you.