Adobe Acrobat Reader freeware by Adobe.
Acrobat Reader allows you to read .pdf files, which, like it or not, are a standard format for documentation. I use this a lot for viewing motherboard manuals. The advantage of an acrobat file is that unlike a webpage it will look the same universally on any platform and it is formatted for printing.

Mozilla Firefox freeware by the Mozilla Foundation.
You’ve come a long way, baby! Now at version 3.0 Firefox remains the king of the alternative browsers. In my opinion, the best overall browser available today. It’s small and fast and has some nifty features. You want to protect yourself from spyware/spamware? I recommend Firefox. pop-up blocking built in and unlike Microsoft Internet Explorer, you computer is not exposed to unsecure ActiveX controls, a favorite exploit of the spam and virus creators. This mozilla based browser is a relatively small to download and install, so there’s no reason not to have it as a backup on your computer.

TIP: If a computer has been infected with a Start Page trojan or is getting so many popups when it gets on the internet that Windows crashes before you can download something to clean it up, I install Firefox to get around these hair pulling frustrations