A few days ago I tweeted the following: "Twitter, please, either let us Instapaper *tweets* with the official clients, or give us private favorites."
It's odd to me that Twitter doesn't offer a way to privately "bookmark" tweets. I want that sort of functionality because I don't always care to reply to someone right away, or want to hold off on retweeting something until some future date. (Twittelator, for example, lets you Instapaper tweets; in fact, it also lets you save tweets to the app itself.)
Karan Varindani replied to my tweet with a great idea: choose "Mail Tweet" and send it to your Instapaper email address. (You can find your address here.) I created a contact named "IP," and gave it my Instapaper email address; the tweet-saving process now takes just seven taps.
It's a simple stopgap that I can't believe I didn't think of myself.