I have collected in a little package some commands I use with beamer to highlight text and math formulas.
Combining the power of beamer with the one of TikZ gives beautiful results.
I have created a collection of commands which use TikZ and its style management to highlight and comment some part of math formulas, and to present for a short moment some text (fleeting box).
This package can be found here as a zip archive: beamerhighlight.zip
The source code is commented and an example tex file is given. I hope that this will be sufficient to understand the commands and the style management. Reading the TikZ documentation could help if you want to get more from these commands.
Any suggestions to improve these commands are welcome.