If I read your post correctly, you can use bitcoin URIs to perform a 'click and donate'.
For example I have a link on multibit.org:bitcoin:1AhN6rPdrMuKBGFDKR1k9A8SCLYaNgXhty?amount=0.1
If you have any of the Satoshi, Electrum or MultiBit clients installed if you click on the link in a browser your client starts up and fills out the send form ready for you to send your bitcoin. I know etotheipi is working on adding bitcoin URI support to Armory so I imagine that will be added to the list soon too.
You will have to fill out any password you have on your wallet (depending on the client) to authorise the payment. A webpage can easily simulate a click on a payment link so you do not want payments to be automatically sent from your wallet without some manual authorisation in your bitcoin client.