Who designed the graphics for your web app, and where did you find them?
sidsavara: I do a lot of development in Java, Java Server Faces specifically. We used RichFaces which comes with some slick templates and modules.  We added FamFamFam silk icons, used JFreeChart for charts and some scriptaculous for transitions and effects, and the whole thing came out looking great.This may be off topic, but I think part of is it the graphics, and part of it is the AJAX "feel".  By that I mean, even though Google Reader and GMail are AJAX apps, they don't "look" like it.  I think that is kind of the point though: they're functional, and they don't get in the way.  We used lightbox type effects, loading buttons and drop downs sparingly, to really enhance the user's experience.