http://www.echofon.com/twitter/iphone/guide.html
Echofon has its own URL scheme. You can add a bookmarklet to Safari to post a link with Echofon. Add the following URL to the bookmarks on your Mac/PC; then sync your iPhone.
Free:
javascript:window.location='echofon:///post?'+window.location
Pro:
javascript.window.location='echofonpro:///post/username?'+window.loaction
