I use imind map which is mindmapping software developed by the bloke who apparently invented mind mapping. It's brillinat and you can try it out for nothing here r presentations and you can  for about a week I think. I'd been shown it by someone else so i just went right ahead and got it so not sure of the trial time. What's good though is that you don't ahve to give payment details for the trial so it doens't just run onto your card if you forget. You can really personalise this software which means you can put links into it, pictures - your own or from their clip art and you can even draw on it. For presentations you can make each bit appear as you want and then link through to other slides and links - it's best if you see the demo and try it out though.