Without a doubt, there are two really excellent programs, which are fairly easy to use, and the possibilities are almost endless.
For the PC, you have
Ulead DVD Workshop 2. You've seen my the first half of my XM set, and that is what I used to create that menu system. JB is another I made in DVDWS2. Almost all of my DVDs are assembled in DVDWS2 these days, I've been using it since the summer of 2004. You can indulge in any number of motion menus, still menus, and various special effects. It's not cheap software, but a few of us are generous to new set creators, if you know what I mean. Guides for this software are going to be posted on here within 2 weeks, both a "basics"
authoring guide and an "advanced"
authoring guide.
For the Mac, you have
DVD Studio Pro available. This is truly professional software, a competitor to something as complex as Scenarist, and based upon the likes of Maestro (outdated, difficult pro PC software). You can literally do anything your heart desires. There are
guides for the older version here, and the newer ones are more drag-and-drop like DVDWS2. Markatisu uses this, and then anybody that has seen the TS 13-DVD set has seen a project done on it. Costs are also not cheap, but same situation as DVDWS2.
Newbies to video all jump up and down saying
TMPGEnc DVD Author (TDA) is the best software, but it's baby garbage for the most part. Allaboutduncan was the only person I have ever seen that could do some decent advanced work in TDA, but the flaws of the software (there are many! they destroy your work!) has even forced him to move to DVDWS2. TDA is fun to learn on, but the menu text will never look good (aliasing errors), linking errors are common, and then audio/video sync is a huge issue with a high probability rate. It's built-in MPEG editor is terrible, sloppy cuts, and known to mess up your a/v sync. This is a warning against getting too attached to it.