I've heard little bits of information about AquaBrowser and thought it was about time I took a closer look. It's a very attractive looking front-end for library catalogues and databases. Features a word cloud. Demo sites are available from the website.
In the same market is Ex Libris's Primo which I have seen demonstrated at Information Online 2007, but there does not appear to be any links to a demo available yet. This has some nice web 2.0 features including tagging and rss feeds.