Every day at 5:00 pm I receive an email from Markus Hohenwarter. It isn't a "hey how are you doing?" kind of email, this one is all business. Actually it isn't even a personal email, it is one of those mass emails that often ends up in the spam box. But more times than not, this spam is worth reading.
Markus Hohenwarter is the creator of GeoGebra which has to be one of my top three classroom tools. The email is generated by the Geogebra upload manager and lists all of the different GeoGebra files (both .html and .ggb) that have been uploaded to the bank during the previous day. Many of the dynamic .html worksheets are ready for classroom use and author attribution is at the bottom of the page. However, if you like the concept of the worksheet but would like to use your own questions, you can download the .ggb file and learn how the sheet was created by viewing the construction protocol.
The only downside to the upload manager is that the uploads aren't tagged, so you have to do bit of hunting to find someting worth while. Regardless, this is yet another reason to love GeoGebra!