This is different from Greasemonkey script. Greasemokey is maybe the best way to integrate google reader and gmail. The fact is that it's a little boring to set up and it isn't working on every browser. This is the simpler way and browser indipendent :D let me know...

1. Click on your Share Button on
Google reader (iGoogle Home
page)

2. Copy Url from http://hosting... to .xml
It will be something like :
http://hosting.gmodules.com/ig/gadgets/file/106269945601404297285/googl
ereader.xml

3. Go to GMAIL → SETTINGS → Gadget
If you do not have gadget button find it
on Google Labs
Paste the url Here, then click Add

4. DONE!
By Alessandro Fontana
afontana.work@gmail.com
http://www.google.com/profiles/
afontana.work