Here's a useful Web-based utility for mobile phone users: 3Guppies. It takes media from the Web or your hard disk, and sends it to your phone. You can use visuals as wallpapers, and music tracks as ringtones.
An embeddable 3Guppies widget will enable the transfer of any image on a Web page to a mobile phone. So if you put the widget on your MySpace page or blog, visitors will be able to to grab all the pictures and videos on it and send them to their own phones. There's also a Firefox add-on that lets you grab any visual on the Web. It's a great way to nab Flickr images for your phone's background.
3Guppies' support of music is limited, but useful. Although the system lets you send visuals to your friends, you can only send music files to yourself, and only as ringtones: There's a little editor that lets you easily select which portion of your track, up to 30 seconds, you want to send over. It does not appear to work with streaming music, only MP3s and other full-file downloads.
The service's real trick is that you don't have to know much about your phone to use it. Anything that 3Guppies can read, you can get to your phone. 3Guppies supports nine video, four picture, and eight audio formats (of course, if your phone can't play video, 3Guppies can't fix that). 3Guppies handles all the transcoding. You don't even have to tell the system what kind of phone you have if you're sending a file to someone else: in most cases, they'll get an SMS or MMS message with a link, and when they navigate to the link 3Guppies will detect what kind of phone the query is coming from, transcode on the fly, and send the right file type back.
The site is in beta, and there are some snags, especially the interaction between 3Guppies.com and the company's previous product, Mixxer, which is part of the service. Login data doesn't seem to transfer between the two Also, the company has not yet finished work on its iPhone support.
Worth a try, though -- especially if you want an easy way to make an MP3 into a ringtone and quickly get it over to your phone. I've embedded the widget below.