I was using Johan's Google Reader Subscribe user script (see the post on his blog) for some time now. I just loved it. The only downside was that it draw a lot of attention and it slowed scrolling down on my laptop. If you've got the same problem you might like Jasper's Google Reader subscribe user script for Greasemonkey. It was designed to use as little screen size as possible. It only adds a feed icon in the top right corner. When you mouse over the feed icon the subscribe links are shown.
I could copy Johan's code but I chose to rewrote the code to experiment with
XPath queries. Man, they are powerful!
Implemented improvement suggested by Chris Wetherell.