The yfrog Twitter image-sharing service can now simultaneously post to MySpace, Twitter and Facebook. You don’t have to go to each website to share that vacation pic you took; just select your image, check the boxes for the services you want to send to and click “Post It!”

yfrog ranked eighth in our Twitter image service user poll two months ago, but it’s been putting up new features slowly over the past couple months, including the ability to post videos and images directly from your webcam. It also powers massively popular URL shortener bit.ly’s image-sharing functionality.

This is a welcome feature, but yfrog isn’t the first to offer something like this. For example, you can do pretty much the same thing with Posterous when it comes to uploading pics to Facebook, Twitter and Flickr. Posterous doesn’t advertise autopost support for MySpace, though, so we suppose you’ll make your decision about which service to use based in part on where your friends are.