Here you have an updated list of free web directories, sorted by Google Page Rank.

1. Librarians’ Internet Index - PR 8
2. Open Directory Project - PR 8
3. Acoona - PR 6
4. Blueboomerang.com, The Online Business Directory - PR 6
5. Busybits Web Directory - PR 6
6. Ezilon Europe - Regional Web Directory and Search Engine - PR 6
7. Free UK Business Directory - PR 6
8. HotFrog US Business Directory - PR 6
9. Iozoo Web Directory - PR 6
10. Jayde – the B2b Search Engine - PR 6
11. Scoot - PR 6
12. Abi Logic Directory - PR 5
13. Bizwy.com - PR 5
14. Canadaone.com - PR 5
15. CANLinks Directory - PR 5
16. Cipinet web Directory - PR 5
17. DirectoryDice.com - PR 5
18. Gain Web - PR 5
19. IllumiRate - PR 5
20. iMegaMall - PR 5
21. Indiamart Business Directory - PR 5
22. Information.com - PR 5
23. Is4profit.com - PR 5
24. Kyotee UK Business Directory - PR 5
25. New Web Directory - PR 5
26. Outsourcing.org - PR 5
27. Prolinkdirectory - PR 5
28. Scrub the Web - PR 5
29. SearchSight.com - PR 5
30. Sphericom - PR 5
31. Surfsafely.com - PR 5
32. Uc33 Web Directory - PR 5
33. Web Central - PR 5
34. Web World Directory - PR 5
35. Where2go.com - PR 5
36. World Site Index Web Directory - PR 5
37. 123india.com - PR 4
38. Abacho.com - PR 4
39. Directory Storm Index - PR 4
40. Directory Vault.com - PR 4
41. e1net.com - PR 4
42. ePagini Business Directory - PR 4
43. ezSearch Directory - PR 4
44. Massive Links - PR 4
45. Megri.com - PR 4
46. Multilingual Search Catalog - PR 4
47. Nerd World - PR 4
48. NetInsert - PR 4
49. oneMission.com - PR 4
50. Pedster Planet - PR 4
51. Resource Central - PR 4
52. SearchtheWeb.com - PR 4
53. SgtSearch Web Directory - PR 4
54. Siccode.com - PR 4
55. Sitetutor.us - PR 4
56. SOCEngine - PR 4
57. TagTooga - PR 4
58. The UK Web Index Directory - PR 4
59. Turnpike Directory - PR 4
60. UK Business Directory - PR 4
61. WebDirectory.co.in - PR 4
62. Wikidweb Directory - PR 4
63. Wow Website Directory - PR 4
64. Zeezo - PR 4
65. ZenSearch.com - PR 4
66. Business B.C. - PR 3
67. Business Services UK - PR 3
68. Details Directory - PR 3
69. Duwf.com - PR 3
70. Ezilon India Web Directory and Search - PR 3
71. Fast Tracked Directory - PR 3
72. Free Directory UK - PR 3
73. Infignos Search & Find Directory - PR 3
74. Link Centre Internet Directory and Search Engine - PR 3
75. Perfext.com - PR 3
76. Poddys Web Friendly Directory - PR 3
77. SearchWarp - PR 3
78. SeekAbove Directory - PR 3
79. Somuch.com - PR 3
80. The Little Web Directory - PR 3
81. The Pegasus Directory - PR 3
82. Tsection Web Directory - PR 3
83. TWB Directory - PR 3
84. US Directory of Search Engines - PR 3
85. UU Directory - PR 3
86. UUIQ Directory - PR 3
87. Webs411.com - PR 3
88. Business Directory of USA - PR 2
89. CherryDir.com - PR 2
90. Etkal.com - PR 2
91. Free Advertising Directory - PR 2
92. Free Business Directory - PR 2
93. SEO Friendly Web Directory - PR 2
94. Shoula - PR 2
95. The Best Links Page - PR 2
96. The Stop@ Business & Home Search Engine - PR 2
97. 9ia.org - PR 1
98. Giant Web Directory - PR 1
99. The Inmeres Solutions Business Directory - PR 1
100. Velendi.com - Free Web Directory - PR 1
101. Websitetop Directory - PR 1

And because we talked about “How Google crawls your site”, I thought that it will be very useful for you, if I make a list with basic Spidering Tools. These tools will help you to understand how search engines see your site.

Multi tools
The Webconfs.com SEO Toolset - you can find here a spider simulator, a redirect checker, a reciprocal link check and more…
The W3C Validation Service - markup validator, link checker, CSS validator
Webmaster Toolkit - search engine spider simulator, link checker, dns checker and more…

Spider simulators
Search Engine Spider Simulator at Self SEO
Spider/Crawler simulator for websites at oyoy.eu - for different user-agents: Yahoo Slurp, Googlebot, MSN, Archive.org and more…

Link checkers
Free Broken Link Checker at Dead-Links.com

DNS Check
DNSstuff - DNS tools, DNS hosting tests, WHOIS, traceroute, ping, and other network and domain name tools.