A few days ago I stumbled the first 100 registered domain name in .com extension so I'm curious to find out the oldest domain in .org .net and .edu extensions. Here's what I've discovered from wikipedia.

Rank Date of registration URL
1. 10-Jul-85 MITRE.ORG
2. 25-Mar-86 SRC.ORG
3. 10-Jul-86 SUPER.ORG
5. 07-Jan-87 AERO.ORG
6. 15-Jan-87 MCNC.ORG
7. 02-Apr-87 RAND.ORG
8. 04-Apr-87 MN.ORG
9. 01-May-87 RTI.ORG
11. 14-Jul-87 USENIX.ORG
13. 03-Sep-87 SOFTWARE.ORG


Rank Date of registration URL
1. 24-Apr-1985 BERKELEY.EDU
2. 24-Apr-1985 UCLA.EDU
3. 23-May-1985 MIT.EDU
4. 27-Jun-1985 HARVARD.EDU
5. 05-Jul-1985 COLUMBIA.EDU
6. 15-Jul-1985 CORNELL.EDU
7. 18-Jul-1985 UIUC.EDU
8. 24-Jul-1985 UDEL.EDU
9. 31-Jul-1985 UMD.EDU
10. 13-Aug-1985 UTEXAS.EDU
11. 20-Aug-1985 USC.EDU
12. 30-Sep-1985 WISC.EDU
13. 30-Sep-1985 UCI.EDU
14. 04-Oct-1985 STANFORD.EDU
15. 07-Oct-1985 UMICH.EDU
16. 09-Dec-1985 UCSD.EDU
17. 23-Jan-1986 ARIZONA.EDU
18. 21-Feb-1986 UCSF.EDU
19. 03-Mar-1986 INDIANA.EDU
20. 19-Mar-1986 UCDAVIS.EDU
21. 19-Mar-1986 VIRGINIA.EDU
22. 25-Mar-1986 UFL.EDU
23. 25-Mar-1986 BU.EDU
24. 08-May-1986 GATECH.EDU
25. 02-Jun-1986 DUKE.EDU
26. 02-Jun-1986 UPENN.EDU
27. 02-Jun-1986 EMORY.EDU
28. 27-Aug-1986 BROWN.EDU
29. 27-Aug-1986 UNM.EDU
30. 04-Sep-1986 WASHINGTON.EDU
31. 08-Oct-1986 NYU.EDU
32. 21-Jan-1987 UMN.EDU
33. 19-Feb-1987 CLEMSON.EDU
34. 17-Mar-1987 YALE.EDU
35. 03-Apr-1987 PRINCETON.EDU
36. 14-Apr-1987 UVM.EDU
37. 16-Apr-1987 NCSU.EDU
38. 30-Apr-1987 UCOP.EDU
39. 27-May-1987 COLOSTATE.EDU
40. 22-Jun-1987 IASTATE.EDU
41. 23-Jul-1987 MIAMI.EDU
42. 18-Aug-1987 UCONN.EDU
43. 24-Nov-1987 FSU.EDU


Rank Date of registration URL
1. 05-Nov-86 NSF.NET
2. 20-May-87 UU.NET
3. 21-Jul-87 SESQUI.NET

Taken from:
http://en.wikipedia.org/wiki/List_of_the_oldest_currently-registered_Internet_domain_names