MyPlick - I have just looked at this site & discovered some wonderful slideshows of my favourite artists like Jan Vermeer. I always check out the Dutch masters whenever I visit large galleries. I always discover something new.

I also like to check out artists I have not seen before, as in the James Ensor Retrospective that was showing at the Museum of Modern Art in New York. MyPlick has lots of artists in its slideshow repertoire.

File conversion - I couldn't immediately think of an application, but then discovered that you could convert a pdf document on the web to a doc format & have it emailed to you. That could be useful. Also there is a video conversion component that enables videos from YouTube to convert to AVI format resulting in clearer higher quality video to watch.