has released an excellent upload plugin for Lightroom 1.3 using the new SDK from Adobe. There are 3 different versions for uploading photos to Flickr, SmugMug and Zenfolio. You can read all about the development here
I've tried the version for Flickr and SmugMug and they both work really well. It makes the process for getting your photos online from Lightroom so simple. I'd definitely recommend installing these if you use any of the three supported photo websites.