QuickerTek, purveyor of coolwirelessaccessories for the Mac, has released a handle for the MacBook (they also have models for other Mac portables past and present). I had one of these years ago on my G4 Titanium PowerBook and I really enjoyed it. It adds a carry handle to your notebook which swivels down to lift the back of the computer off your desk when you set it down. This supposedly improves the typing angle and also improves heat dissipation (thus saving you from scalded thighs and, if one of those ubiquitous "studies" is to be believed, maybe even sterility!)
In any case, it looks like it could be a handy product for MacBookers on the go, but I wonder how it might interfere with your sleeve or case.