While Jakob Nielsen, Tog, and many others have great advice, one needs to be mindful of publication dates. I haven't read Tog's books and have no doubt they have good information, but as they were publised in 1992 and 1994, there will be material that isn't applicable today.

One also needs to take into account differences between Web and desktop apps. The desktop UI is typically richer, provides more functionality, and is more responsive to the user.

>Hi David,
>
>jumping in here: I hope Tamar and Craig convinced you that a "uniform interface" is the worst possible choice. <s>
>
>Hopefully you have included Tog books in your list (http://en.wikipedia.org/wiki/Bruce_Tognazzini).
>
>Think iPhone: our sales guy, who can barely use our software, opened his iPhone box, didn't read the directions, and was happily using it in 5 minutes, including having downloaded his old contact list. That's what Tog means when he says "appliance": something as easy to use as a toaster.
>
>For Power Users, the idea of OLAP is as easy for them as the iPhone was to our sales guy. The more options you make easily available with a click or two, the happier they will be.
>
>The general advice on design is: define your users by type, including writing storyboards that take them through their use of the software, written as a story. If they are currently doing this type of work, watching them and after having watch them, talking with them, will help you this task. Only then, define the interface that would be ideal for each user. Then mock them up (e.g., with SketchFlow or some other tool), and try them out with the users of each type. You'll still have to watch them do the task on the alpha of the interface, because they won't know everything to tell you, and you won't have know everything to look for, but at least you'll be in the right ballpark.
>
>Hank