A quality webquest will have many of the characteristics you described during the 100 facts exercise. They are inquiry based, utilize high level thinking skills, have students performing meaningful tasks, and utilize the internet in an authentic way. There are thousands of webquests published on the internet by teachers and lesson plan designers, but not all of them are of high quality. When choosing a webquest, take a look at the rubric that goes with it. What are students being evaluated on? This is a quick way to get an idea of the process skills and thinking skills involved in the webquest. Another indicator of a high-quality webquest is if it includes a teacher page with more thorough directions and resources.
Then, take a look at the rest of the webquest to see if it meets your needs and requirements. Check all the links in the webquest to see if any of them are "dead." If the webquest requires the use of specific software, make sure that software is available to you on your campus. If it's not, check if there's a comparable program or application that would still meet the requirements of the webquest. Check to make sure the task and process are appropriate for your grade level. If you feel that you've found a quality webquest, but it doesn't meet your needs exactly, you can always tweak it a little, or at the very least, use it as a jumping off point for writing your own webquest!
Here are some links to lists of high quality webquests.
Page that lists webquests by grade level and subject area.
webquest.sdsu.edu/ - This is an excellent resource for searching for webquests as well as building your own.
bestwebquests.com/ - another good site for searching for webquests.
