I started off with a stacking two bike holder like yours caligurl. That is up against the wall of the garage and usually holds my two bikes. When my BF moved in along with his 5 bikes (plus a frame that isn't built up), I told him that he needed to find a way to store them that still allows the cars to be in the garage. The frame went in the attic and an old, beater commuter bike is leaning against the fence outside. For the other 4 bikes, he put hooks in the ceiling and hangs them from the back wheels. He even re-arranged things so that his workbench, etc is along the back wall of the garage underneath the bikes. It's a pretty impressive set-up... looks like a mini bike mechanic shop.
Of course, you can't ever have enough bikes. He just bought another frame off e-bay that he wants to build up. He is struggling with how he will store it or what bike he will give up to make room for it.
2004 Colnago Chic - WTB Deva
2008 Blue RC7 - WTB Deva
2009 Colnago Master X-lite - WTB Deva