This page includes links to useful tools and resources for WordPress plugin developers.
Software
TortoiseSVN – Freeware Subversion (SVN) client for managing project files and folders in the wordpress.org site.
Notepad++ – Freeware styled text editor
WinMerge – Freeware file comparison utility (integrates into TortoiseSVN)
Paint.NET – Freeware photo image editor