I am looking to create a list of assignments using Web 2.0 that could be completed in 20 minutes or less. I am new to the idea of using these tools with children and would appreciate any ideas you might have.
Why Web 2.0 and less than 20 minutes??? What's your goal? Collaboration, communication, or just learning the tools.
If you want kids to discuss part and forth I would recommend VoiceThread
If you want them to collaborate ideas consider Wikispaces or Google Docs
If you want them to share photos check out Animoto or Flickr or FlickrStorm
If you want to practice orally speaking - make a Voki or create a podcast with Audacity
If you want them to share in a creative way - pick a theme and make a Glogster or Photoshow
If you want to play with words make a Wordle
You can always find tools to do something - start with the goal in mind first and then find the appropriate tool to meet the need.
With training you can have students create a three panel cartoon on ToonDoo in about 20 minutes (those can also be uploaded to blog sites). I am going to highly stress the training part. I made a cartoon this weekend and it took me forever because I was so busy playing. Once I gave myself a mental slap for wasting time I started to use the search feature for the cartoon features I wanted and it went by much quicker. I am on the fence how I would use this in my classroom, hence the practicing this weekend but I understand one elementary school is using them in our district to enhance her reading and language arts lessons. You can check out my cartoon book (which is a series of cartoons put together into a book format on my students blog at www.mrsheatonsclass1.blogspot.com just click on it to make it bigger). A book would take more then 20 minutes - although if you get a group of students working on separate sections of the book it might work.
I am assuming you are running your students through centers? I did this with an elementary class and decided that I would do a week of centers as opposed to rotating during one class period. That gave me and the students more time.
The centers were as follows:
#1 - Track a hurricane and answer questions related to the tracking
#2 - Mix and Match Water Cycle tags and create an interactive poster
#3 - Create a weather safety poster
#4 - Hurricane Webquest on the Computer
#5 - Small group with teacher working on a notebook assignment
It was time consuming to set up but the kids loved knowing that they were roating to the next thing when they came into class that week. I recruited a parent volunteer to help with the hurricane tracking station with my less focused group. I ran into a snag because I miscalculated a school activity on Friday and was cut short. So I might make my centers Monday-Thursday with a Friday makeup day.
My experience with technology, in general, is that there are very few less than 20 minute assignments (especially when you are working with 30 students and trying to introduce something new)... You can break assignments into chunks...
There is a wiki that has been set up by Wendy Drexler in Florida. It's http://teachweb2.wikispaces.com/ and has a lot of tools and ideas. It is an open wiki where people can contribute ideas for using various tools. There is also a SWOT analysis (strength, weakness, opportunities, threats) section. Although it does not suggest time frames, you may get some ideas on the wiki.