Software

1581-Copy
CBM 1581 floppy disk copy utility for DOS. Imports and exports 1581 disks to a PC based 3.5" floppy drive and disk controller.
http://d81.de/

DirMaster
Windows-based tool for the management of emulator formats (.d64, .d81, .d2m, etc) and archival formats (.arc, .sda, .lnx, etc)
http://www.style64.org/index.php?cid=rele.dirmaster

Final TAP
Tool for working with digital copies of .TAP cassette files.
http://www.coder.pwp.blueyonder.co.uk

gui4cbm4win
Graphical front-end to cbm4win which allows user to read/write to real serial Commodore floppy drives (1541, 1571, etc) under Windows 2000 or XP.
http://www.jammingsignal.com/gui4cbm4win/

LNG: LUnix, the Next Generation
An experimental operating system for the Commodore 64/128. The open source project is hosted at SourceForge and has been ongoing since 1993.
http://lng.sourceforge.net/

The Turbo Assembler (for C64) Homepage
Online home for native C64 Turbo Assembler, Turbo Macro Pro, modifications, and related tools.
http://turbo.style64.org/