Top 100 Tools for Learning 2009, compiled from the contributions of 278 learning professionals, by Jane Hart:
"The tools that moved up the list this year. Note although Twitter moved up 10 places this year to become the top tool, in fact there were other tools that moved up even more places, e.g. YouTube has jumped 15 places to come in at 3rd place, Slideshare up 13 places, and Google Apps and Bubbl.us moved up 28 places."
References:
Top 100 Tools for Learning 2009: The Final List. Jane's E-Learning Pick of the Day.