CSS Type Set
Font Tester is a free online font comparison tool. It allows you to easily preview and compare different fonts side by side with various CSS font styles applied to them.
Em Calculator is a small JavaScript tool which helps making scalable and accessible CSS design. It converts size in pixels to relative em units, which are based on a text size, by Piotr Petrus
The Typetester is an online application for comparison of the fonts for the screen.