Bike Storage
I would hang it from both wheels. It won't hurt it at all to hang it from one or the other, unless the kids are hanging on it and stuff (even then, it probably won't hurt anything). I'd get two of these, screw them into the ceiling, and hang it upside down from both wheels.

"The melting point of wax means nothing to me": Thrice
I bought one of the cheap ($20) bike stands from Nashbar. It isn't very sturdy but it works by simply laying the seat stay over it. It can be used for chain cleaning and other simple maintanence.
I bought the ones from that get bolted to the ceiling and use ropes to hoist the bikes up. It hooks onto the handebars and under the saddle and has been very useful for me. I found one of the advantages was that it was the wheels hanging down which take up a little less airspace than when the handlebars hang down.
http://www.target.com/Ceiling-Bike-Lift/dp/B00006JBL3/sr=1-1/qid=1202324...
That's the unit. I ended up with 2 of them and have been very happy with how they work.
To tri or not to tri - that's not a question at all!
I use those S hooks but hang it from the top tube.
I have a softride so the frame does not lend itself to hanging from the top tube. I bought an Ikea bike rack and hang it vertically from one wheel (either the top or bottom, don't really pay much attention to which one goes up first). Do you really think that hanging a 20 pound bike by one wheel will do more "damage" to a wheel than a 150lb-200lb rider would while encountering every day road obstacles? Technically speaking, the bike is hanging from the underside of the top of the wheel - by the spokes - when you are on it anyways.
I have all my bikes hanging by one wheel. Just simple S-hooks like mentioned above. Been that way for a long time and never had a problem. As was said above, if a wheel gets damaged by hanging a 20 lb bike, storage isn;t your biggest issue.





I was wondering what everyone thinks of hanging your bike by either the front or rear wheel? I have limited space inside my house (five kids takes up pretty much everything) and I want to get my bike up in the air in the basement so it isn't being knocked over all the time, but I'm worried that hanging all the weight off the wheel will cause it to warp. What say you, Trifuelers?