Nr. 1: Wolfram|Alpha

Wolfram|Alpha

- computational knowledge engine.

Nr. 2: AlternativeTo

alternativeto

- Find better Windows, Mac, Linux and online applications.

Nr. 3: fontcapture

fontcapture

- create a font from your very own handwriting.

Runners-Up:

Command-line Fu Command-line Fu

- the place to record those command-line gems that you return to again and again.

HootSuite HootSuite

- manage multiple Twitter profiles, pre-schedule tweets, and measure your success.

mockingbird mockingbird

- an online tool that makes it easy for you to create, link together, preview, and share mockups of your website or application.

browser-size browser-size

- Google Browser Size is a visualization of browser window sizes for people.

Google Fast Flip Google Fast Flip

- Google Fast Flip is a web application that lets users discover and share news articles.

Google Wave Google Wave

- Google Wave is a new model for communication and collaboration on the web.

idaft idaft

- the Daft Punk’s console.

Full list (ranked by the number of bookmarks at delicious):

  1. wolframalpha (20947 bookmarks)
  2. alternativeto (6463 bookmarks)
  3. fontcapture (5435 bookmarks)
  4. commandlinefu (5001 bookmarks)
  5. hootsuite (4411 bookmarks)
  6. mockingbird (4120 bookmarks)
  7. browser-size (3626 bookmarks)
  8. google-fast-flip (3623 bookmarks)
  9. google-wave (3600 bookmarks)
  10. idaft (3380 bookmarks)
  11. colorotate (3098 bookmarks)
  12. wearehunted (2792 bookmarks)
  13. google-news-timeline (2676 bookmarks)
  14. dropular (2661 bookmarks)
  15. bespin (2602 bookmarks)
  16. measurement-lab (2502 bookmarks)
  17. google-squared (2337 bookmarks)
  18. yuml (2281 bookmarks)
  19. typekit (2258 bookmarks)
  20. open-atrium (2069 bookmarks)
  21. google-similar-images (2028 bookmarks)
  22. open-web-tools-directory (1996 bookmarks)
  23. clicker (1900 bookmarks)
  24. freetwitterdesigner (1854 bookmarks)
  25. ixedit (1803 bookmarks)
  26. google-page-speed (1773 bookmarks)
  27. fotopedia (1725 bookmarks)
  28. serverfault (1655 bookmarks)
  29. collecta (1653 bookmarks)
  30. storybird (1630 bookmarks)
  31. square (1607 bookmarks)
  32. photopeach (1583 bookmarks)
  33. axiis (1578 bookmarks)
  34. google-image-squirrel (1517 bookmarks)
  35. nearby-tweets (1498 bookmarks)
  36. jetpack (1387 bookmarks)
  37. blind-search (1381 bookmarks)
  38. exectweets (1355 bookmarks)
  39. truecar (1334 bookmarks)
  40. photovisi (1298 bookmarks)
  41. wibiya (1204 bookmarks)
  42. twitterjobsearch (1199 bookmarks)
  43. xmarks (1162 bookmarks)
  44. recipepuppy (1159 bookmarks)
  45. stimator (1157 bookmarks)
  46. hotgloo (1157 bookmarks)
  47. scr.im (1099 bookmarks)
  48. tweeteffect (1072 bookmarks)
  49. filesovermiles (1065 bookmarks)
  50. skimmer (1063 bookmarks)
  51. cloudantivirus (961 bookmarks)
  52. conceptfeedback (947 bookmarks)
  53. tinker (937 bookmarks)
  54. cramberry (919 bookmarks)
  55. notable (908 bookmarks)
  56. tweetboard (901 bookmarks)
  57. docjax (886 bookmarks)
  58. artbabble (851 bookmarks)
  59. mysocialbuttons (833 bookmarks)
  60. babelwith (811 bookmarks)
  61. magma (810 bookmarks)
  62. spezify (805 bookmarks)
  63. tomsplanner (802 bookmarks)
  64. brizzly (793 bookmarks)
  65. psykopaint (788 bookmarks)
  66. tweepsearch (779 bookmarks)
  67. twendz (777 bookmarks)
  68. packwhiz (772 bookmarks)
  69. booster (762 bookmarks)
  70. linguee (761 bookmarks)
  71. klout (757 bookmarks)
  72. tweepler (745 bookmarks)
  73. top-twitter-friends (726 bookmarks)
  74. supalogo (716 bookmarks)
  75. twitterhawk (715 bookmarks)
  76. wetransfer (704 bookmarks)
  77. yardsaletreasuremap (702 bookmarks)
  78. twitlogo (694 bookmarks)
  79. tagul (675 bookmarks)
  80. newssift (675 bookmarks)
  81. moleskine-msk (657 bookmarks)
  82. tonido (652 bookmarks)
  83. herdict-web (651 bookmarks)
  84. refollow (644 bookmarks)
  85. tweetpsych (634 bookmarks)
  86. untweeps (619 bookmarks)
  87. scripty2 (618 bookmarks)
  88. twitblock (615 bookmarks)
  89. nanocrowd (610 bookmarks)
  90. eyeplorer (607 bookmarks)
  91. bingtweets (588 bookmarks)
  92. all-for-good (582 bookmarks)
  93. tweetphoto (578 bookmarks)
  94. su.pr (575 bookmarks)
  95. goby (574 bookmarks)
  96. focusbooster (574 bookmarks)
  97. livingstories (572 bookmarks)
  98. joobili (569 bookmarks)
  99. loop11 (566 bookmarks)
  100. yahoo-placemaker (561 bookmarks)

See the Betas of the Year from 2005, 2006, 2008 and 2010.

See also the Class of 2004, 2005, 2006, 2007, 2008, 2009 and 2010.