2xExplorer
Dual-pane alternative to Windows Explorer, packed with useful features. The original, free version is still available but has been replaced by a redesigned, commercial app called Xplorer2.
Avant Browser
Tabbed browser based on MS Internet Explorer. Many additional features. Free.
Firefox
Tabbed browser from Mozilla, offering good web-standards compliance plus every feature you are likely to need. Free.
KeePass
Excellent open source password safe. Now that we've moved away from the 'one password for everything' approach we use this all the time.
Maple
This is an outliner. Don't know what an outliner is ? Well, it's kind of a structured, hierarchical organiser, or maybe it's a text manager, or possibly a brainstorming aid. Whatever, this is a good one - yours for around $20.
MP3 Tag
In our search for a decent MP3 tag editor we found a lot of second rate, shoddy software. In contrast, this one is well written and easy to use.
Notepad2
Replacement for the standard Windows Notepad application, offering many useful new features. There are no end of free Notepad replacement apps on the net. This one is the best.
SyncBack
File/folder backup and synchronization application featuring (among many other things) multiple folder support and FTP functionality. Unusual but effective user interface. Freeware.
Topstyle
Excellent CSS and HTML editor. Used to hack together this very site (not that that's much of a recommendation). Yours for around $50.
TreeSize
Provides a disk usage overview for any specified folder. Integrates with the right click menu. Fast, efficient and free. (We were going to write something similar but really, this is so good it's not worth it.)
WinMerge
File / folder comparison tool, with a nicer interface than, for instance, WinDiff.