For MAc you may want to try
Fotomagico, It is getting rave reviews everywhere and you can burn HD,DVD, Ipod, etc. They just came out with a new version and you can try it for free.
iPhoto is ok and iDVD can do slide shows, specially if you are using Aperture. When you open iDVD you can see your Aperture library.
On a PC, I think ProShow Producer is one of the best. I don't care much for its DVD buring feature and I use Adobe Encore to do my DVD and menus.
Showitweb is exactly for that, the web, but the new version 2.5 has a feature that you can have Dj make a DVD for you. You may want to check that also.