I read all my feeds in the awesome RSS feed reader for Mac,
NetNewsWire. It usually allows you to post to Delicious either via a
keyboard shortcut or right-click. Here is how to post to Pinboard
inside NetNewsWire:

Go to your Pinboard howto page. Right-click the 'same page'
bookmarklet and choose Copy Link.
Paste the link in a text editor (preferably Text Wrangler) and save as
pinboard.js
Copy pinboard.js to Library > Application Support > NetNewsWire >
Scripts

Now you can bookmark any page open in NNW to Pinboard by going to
Scroll icon on the menu bar (left of Help) and clicking on pinboard.js
option.

If you want to assign a keyboard shortcut, you can do it via Mac's
System Preferences > Keyboard > Keyboard Shortcuts > Application
Shortcuts (on the left bar). Add 'NetNewsWire' application in the list
if not yet available and add the shortcut to pinboard.js. I used Shift
+Cmd+P but you can assign anything.

Voila! That's it. Open a page in NNW and hit your shortcut and post to
Pinboard.

Somehow the script for Popup bookmarklet doesn't work. Also, I don't
know how to add this to the right-click option in NNW. If anyone does,
it is as good as Delicious for quick bookmarking.

PS. Selecting the text before bookmarking puts the text in the
Description field for Pinboard but doing the same doesn't put it in
for Delicious. Go figure!