I recently came across this site, http://www.slideroll.com and i am probably the last one to do so! Found it extremely interesting. Slideroll helps you create online slideshows. The membership is free and it allows storage of a sufficiently large gallery of pictures. Slideroll enables one to add music to the slides from a given list of tunes from different genres you can choose from. There are also options for text slides, zoom, timing etc.
Unfortunately there is no option to add/upload music files from your pc (I didnt find it). Another issue I faced was embedding the slideshow in wordpress. There were many codes for embedding, but noting was working on my wordpress. I spent a lot of time and brain exercise trying to figure out what the code meant. No luck! But I came across an interesting feature to solve all these problems. There is a free slideroll video creator, which you can download to your pc and attach slideshows created on the site and upload music from your pc. The end result is an mpeg file that can be uploaded to youtube and google videos and even to wordpress.
So here goes my first slideshow using slideroll video creator. It is a collage of some photos I clicked during our trips around US. Check out –