I park mine in a 1% savings account until tax time comes. There might be ways to have slightly higher expected return (bonds?) but its easy, simple, and better than leaving it in checking earning nothing.
Moving it to savings also gets it out of my view as I don't have that account connected to Mint. In my mind its already gone so it doesn't hurt as badly when I have to write 5 figure checks to Uncle Sam every few months. Also makes it less likely that I'll feel "rich" and be less motivated or more spendy.
