The scary thing is I use these every now and then!

41. Act naturally
40. Found missing
39. Resident alien
38. Advanced BASIC
37. Genuine imitation
36. Airline Food
35. Good grief
34. Same difference
33. Almost exactly
32. Government organization
31. Sanitary landfill
30. Alone together
29. Silent scream
28. Living dead
27. Small crowd
26. Business ethics
25. Soft rock
24. Military Intelligence
23. Software documentation
22. New classic
21. Sweet sorrow
20. Childproof
19. "Now, then ..."
18. Synthetic natural gas
17. Taped live
16. Clearly misunderstood
15. Peace force
14. Extinct Life
13. Temporary tax increase
12. Plastic glasses
11. Terribly pleased
10. Computer security
9. Political science
8. Tight slacks
7. Definite maybe
6. Pretty ugly
5. Diet ice cream
4. Rap music
3. Working vacation
2. Exact estimate

And the Number One Oxymoron is :

1. Microsoft Works