Today, I wanna talk about the most popular directories and search engines. So Every one can ask me: How do you know that SE or Directory are popular or now, and how to make difference?
The answer is so easy. First, you have to know that the big strong tool to differentiate is Google PageRank and Alexa.

Page Rank Checker is a free tool to check Google™ page ranking of any web site pages easily and to display your site's PageRank™ value on your web pages

http://www.prchecker.info

Also, I find Alexa is helpful in orde to check classfield directories.

http://www.Alexa.com

This a list of Search Engine/ Director from www.sitesubmiturl.com

Search Engine/ Directory
1. Google 2. Yahoo! Search 3. Open Directory 4. Bing 5. SearchMe 6. ScrubTheWeb 7. Cuil 8. ExactSeek 9. SearchSight 10. EntireWeb 11. LII 12. Web World 13. A1 Web Directory 14. MavicaNet 15. Dramba 16. Link Centre 17. What U Seek 18. Wikidweb 19. IllumiRate 20. Arakne Links 21. Domaining 22. BusinessSeek 23. Directory Storm 24. Info Listings 25. Pedsters Planet	1 2 855 1,547 3,934 11,637 13,620 15,134 15,195 16,515 21,635 25,413 26,014 26,345 27,086 28,222 28,349 28,409 28,660 28,907 28,999 29,841 30,361 30,461 30,520	10 9 8 2 7 6 7 3 5 6 8 3 4 4 3 3 6 4 5 4 3 3 4 4 4

Search Engine/ Directory
26. My Directory Live 27. Info Tiger 28. Ablaze Directory 29. SurfSafely 30. Search Web World 31. World Site Index 32. Exalead 33. 01WebDirectory 34. IS 35. AMRAY 36. Finest 4 37. CyberWebSearch 38. The Living Link 39. SonicRun 40. TowerSearch 41. IWD 42. Web Linker 43. Web Directory 44. Wondex 45. OneMillionDirectory 46. NetInsert 47. Clock Tower Studio 48. Cipinet 49. Amidalla 50. Amfibi	30,614 30,756 31,256 31,708 32,677 33,725 36,380 36,475 38,583 38,814 40,296 40,992 41,887 42,190 42,855 44,162 44,722 46,523 47,052 47,696 49,095 52,629 54,620 56,658 56,740	4 5 4 5 4 4 7 0 4 3 2 4 3 4 4 5 0 0 2 2 5 3 4 4 4 4