Zoomit and NLarge are two great tools that can be utalized when doing presentations, each allow you to draw onto the screen to highlight various points of intrest to your guests.
This makes a presentation even more interactive and makes the crowd really feel part of the action. Both have functions allowing you to zoom into the screen, which is especially useful when giving a code demo and you want to get across the importance of a section of code.
Guy Smith Ferrier (Microsoft MVP)discusses both of these peices of software in his blog post NLarge Vs Zoomit, with the opinion that Zoomit is the better of the two products.
Give the software a download and make up your own mind. I for one really like the extras that the software adds to a presentation.