Thanks everyone for your replies. I practically have this web app complete now but it looks shitty in some places and inconsistent in others - I purposefully never lingered over presentation aspects and instead concentrated on functionality.
I soon need to show my wares to the boss and (sadly) I know that his first impressions will be based more upon appearance than technical accomplishments. In short, I need to add Style sheets to my app to pretty it up. Not only that, but on behalf of it's users, they also need an intuitive colour styling too.

I have read some pretty interesting theoretical stuff on this page indirectly from one of dz33y's links:

In visual experiences, harmony is something that is pleasing to the eye. It engages the viewer and it creates an inner sense of order, a balance in the visual experience. When something is not harmonious, it's either boring or chaotic. At one extreme is a visual experience that is so bland that the viewer is not engaged. The human brain will reject under-stimulating information. At the other extreme is a visual experience that is so overdone, so chaotic that the viewer can't stand to look at it. The human brain rejects what it can not organize, what it can not understand. The visual task requires that we present a logical structure. Color harmony delivers visual interest and a sense of order

- but I haven't got the time to apply these ideas and derive something completely original...

I need something ready-made with application examples that I can quickly skin my app with - any ideas (please)?