Remote Antenna Switch
Since the backyard is out, I've got two plans of attack that I'm working on, and I'll probably end up using both. They both involve using the wooded area behind the backyard. One plan involves buried coax and a remote antenna switch. The other involves a temporary (i.e. removable) segment of ladder line. Each has its upsides and downsides.
Tom, NE1R, advised that I go out and buy a Harley -- the idea being that compared to that, a wire across the back yard really isn't such a bad thing.
Anyhow, I have finished the remote part of the remote antenna switch (see 2007 ARRL Handbook). The article was right that the most difficult part was drilling all the holes so that everything lines up! Here are a few pictures:

The enclosure is (was!) a watertight box with a gasket and latches, but now that I've gone and drilled into it...

This will mount to a 4x4 post behind the rhodies in the back of the back yard. An office type trash can will be used to help protect it from the weather.

Next on my list is to order some coax, ladderline, antenna wire, and other
miscellaneous bits from Davis RF.
Update: placed the order on 26 Sept, 2007
Another update: received order
Yet another update: XYL is preventing *any* outdoor antennas :-\ I'm waiting for that giant beer can to land on me...