One of the neat things about Google Books is that I can keep track of my library digitally (I can do the same with Library Thing as well). One thing I would really love to have is a similar system for my journal articles. The main reasons for this is the fact that I have a large number of journal articles photocopied and it is kind of difficult to keep track of them (other than the fact that I keep them in huge pile rather than trying to sort them). If anyone knows of such a thing, please let me know.
What would be really neat would be to have a system that hooked into Bibtex so that it would automatically add a hyperref link to the article online rather than just to the bibliography at the end of your book/article.