sysinternals - bought by Microsoft, but still excellent low level tools.
defrag - better defrag from Dave Whitney.
mcse world - very good Windows knowledge base by Daniel Petri.
sql skills - ms sql knowledge from the ms sql legends.
sql dts - great resource for integration services.
connectionstrings - use ado to connect to just about any data source.
upx - very clever tool to compress binary executables.
xdelta - very cool open source byte-level-differencing.
bsdiff/bspatch - linux byte-level-differencing optimised for executable files. There is a link to a Windows port, and there is another one here compiled with bzip2:

Web graphics
cooltext - long standing button and logo generator.
roundedcornr - generates very good corners.
wellstyled - colour scheme generator.
gradient image maker - my generator of choice from dynamicdrive.
the amazing gradient generator - pretty good generator.
buttonator - button generator.
mycoolbutton - good button generator.
glassy buttons - another button generator.
ajax loader - some nice ajax wait animations.
web logo creator - fun.
stylr - another logo generator.
pixel button - good generator for pixel buttons.
background image maker - pretty flexible.
stripe generator - very cool generator!
embedded media html generator - generates the html to embed media files in your web page using wmp.

winuae - i loved my amiga 500 and 1200 - now they live again on the PC platform.
back 2 the roots - the ultimate download site for old skool amiga games, demos, and apps.

Sites I built
neptune supplies - 2003.
owlsbury osteopaths - 2008.

Free/Open Source
utorrent - excellent lightweight client.
dvd shrink - compress dual layer movie to single layer size for backup.
7-zip - Excellent open source compression.
truecrypt - Excellent open source on-the-fly encryption.

Free OS
puppylinux - Small, boot from CD, USB, or hard disk.
CentOS - Server OS of choice - basically Redhat.
ubuntu - Desktop OS of choice.
damn small linux - Small, boot from CD, USB, or hard disk.

virtualbox - From Sun Microsystems but open source. Desktop virtualization with cool seamless mode.
xen - Open source industry standard hypervisor.
Microsoft Virtual PC - Desktop virtualization - I use this a lot. Free from Microsoft.
Microsoft Virtual Server - Server virtualization. Free from Microsoft and very cool.
VMware - Server, desktop and hypervisor virtualization products - some free, some not.