Start with the basics.
Take a look at whatever basic CMA data is output by your MLS system. Here in California, we have an add-on software package called CMA Pro that links up with MLS search software and lets us create some pretty amazing listing presentations. At the more basic level, there is a QuickCMA feature built into the online version of our search tool that just gives a really basic CMA.
Now, I have used lots of things in the past to create listing presentations. I started off with Powerpoint, moved on to CMAPro, now I am putting together a listing presentation using Keynote 3 on the Mac.
If you go the digital route for doing your listing presentations, just remember to ALLWAYS print out your listing presentation in case your technology leaves you hanging.
When you walk into the listing presentation, you should have your laptop, one of those presentation style binders (they stand like an A frame and let you flip pages over the top) and a nicely but inexpensively bound version for your sellers, if you do that sort of thing. You only need the presentation style binder if you computer fails or for some reason not everyone can see your computer screen at one time.
As for leaving your listing presentation with the seller, some agents don't think this is a good idea. They feel like they may be giving something away if the sellers show it to other agents, etc.
I usually do not leave the whole presentation with them, but I do leave a summary with all the basic info and conclusions. I do this more to make it easy for the seller to review the info than for any worries over confidentiality.
R