just have the noStrudel logo in the upper left corner toggle between logo and donate button.

when a user donates ask them when they want to be reminded to donate again ( 1 moth, 3 months, 1 year ) and they won't see the "donate" button again until then. 

 ooh, I like the reminder idea. 
although I don't think the logo is a good place. I like the fact that it always goes to the home page, I use it all the time :)