Nifty tools for windows
Here are a couple useful tools for windows.
XP Remote Desktop client. It's much better than the RDP client that comes with 2000, as it can be maximized.
TamperIE (download). An IE plugin that allows to intercept POSTs and GETs before they occur and gives you a chance to tweak it (change/add POST data). Unfortunately, I couldn't find the product page for this tool. Activate it with scroll lock.
Web development oriented bookmarklets. Notice the javascript shell and the interactive CSS style testing bookmarklets, they are really great for interactive web development. The only problem is that these two don't work in IE (probably because of the stupid 508 character restriction that appeared in IE6.0) and frames (this can probably be fixed).
Sysinternals freeware tools. Very useful system tools for Windows, including a process explorer that lists all the open files per process (Process Explorer), a remote process launcher (psexec in PsTools) and more.
Ngrep. A free and simple command-line sniffer utility, base on Pcap and winPcap. There is also a GTK+ based front-end named Ethereal, that is cross-platform.
Of course, Mozilla is one of the best tools for web development. This article describes how to use it in testing and debugging web sites.
Synergy, a cross-platform software KVM, that allows transparent mouse and keyboard sharing across multiple computers.
Update: The TamperIE folks came up with another tool: Fiddler.
"Fiddler is a HTTP Debugging Proxy which logs all HTTP traffic between your computer and the Internet. Fiddler allows you to watch HTTP Traffic, set breakpoints, and "fiddle" with incoming or outgoing data."