Basics
1. Windows Vista OS to Ubuntu OS
2. Internet Explorer Browser to Firefox Browser
Office Suites
3. Microsoft Office to OpenOffice
4. Mactopia to NeoOffice
Office Tools
5. MathWorks MATLAB to Scilab
6. Microsoft Access to Kexi
7. Microsoft Word to OpenOffice Writer
8. Microsoft Excel to OpenOffice Calc
9. Microsoft Visio to Dia
Productivity
10. Blackboard to Moodle
11. Box to Cabos
12. Microsoft Project to Open Workbench
13. Mindjet to FreeMind
Graphic Programs
14. Adobe Illustrator to Inkscape
15. Adobe PhotoShop to GIMP
16. Adobe Premiere to Avidemux
17. AutoCAD to Archimedes
18. Microsoft PowerPoint to OpenOffice Impress
19. Microsoft Paint to Tux Paint
Web Editors
21. Adobe GoLive CS2 to Mozilla SeaMonkey
22. Adobe Dreamweaver to NVU
23. Macromedia Flash Professional to OpenLaszlo
24. Microsoft Frontpage to Bluefish
25. Windows Notepad to ConTEXT
26. Altova XMLSpy to XML Copy Editor
Publishing
27. Adobe Acrobat to PDFCreator
28. Adobe Framemaker to DocBook
29. Microsoft Publisher to Scribus
Communications
30. AIM to Pidgin
31. FeedDemon to RSS Bandit
32. Microsoft MSN Messenger to aMSN
33. Microsoft Outlook to Thunderbird
34. Skype to Wengophone
Media
35. iTunes to Songbird
36. Nero Burning Rom to K3b
37. Quicktime to Darwin Streaming Server
38. TiVo Desktop to Galleon.tv
39. Windows Media Player to Miro
Utilities
40. CuteFTP to Filezilla
41. iBackup to ZManda
42. Norton Ghost to Partition Image
43. Rational Purify to Valgrind
44. WinZip to 7-Zip
Security
45. Kaspersky Anti-Virus Personal to Winpooch
46. McAfee VirusScan to ClamWin
47. Norton Personal Firewall to WIPFW
Financial
48. Authorize.net to OpenSSL
49. Microsoft Money (Plus) to TurboCash
50. Quickbooks to Compiere