https://www.citethisforme.com/ - I think this is what Rosa meant

Allows for having different classes, public and private test, etc. Very well organized!

http://www.medcalc.org/calc/diagnostic_test.php - there are some free stat calculators avaiable here

http://www.quantitativeskills.com/sisa/ - and even more here

For those who haven't participated yet, please keep track on the on line courses offer at Stanford, and when you have the opportunity, you must take the Writing in Science course. Really, really, really great adventure - after completing you'll just not be able to wait to write your next paper.

Very user friendly free chemistry database: chemicals 2D and 3D structres, most important characteristics ect