Yes, most of these sites will allow you posting HTML one way or another. Like in MySpace you can post the HTML in your profile. In FaceBook, you can use an FB application to let you post any HTML in the app window in your profile. Please note, that while generating buttons in E-junkie, you will need to uncheck the box which says "uncheck this box if you need non-js code for pasting in myspace and similar sites".
If you are selling on blogger or your own blog or site, you can simply paste our regular code in there.
If you are selling on craigslist or selling on flickr or a forum or maybe selling using your skype status message, where the only think allowed is a link, then you can simply take the URL from our purchase buttons and use that.
