Lots of bikes? Want your floor space back? Some (big) scrap lumber, a drill, a couple screws and some hooks are all ya need.
Nekkid wood will work fine, but I felt like painting these for some odd reason.
First, find the studs in your wall, and mark them.
Second, figure out how high up the wall you want to attach the board. Measure or at least estimate the overall length of your bikes. you will want the board to be at least this high.
Next, grab a 2xwhatever's handy it needs to be long enough to fill the wall space you are working with and short enough to fit on the wall.
Attach the board to the wall with the screws, longer screws will make a more sturdy finished product.
If you want you can hang another board above the first, this will roughly double the amount of bikes your wall will hold.
Drill pilot holes in the 2x and screw in the hooks.
If you opted for the two board method, you will want to stagger the hooks so that your top row of bikes hang between the bottom row.
Hang bikes and enjoy all that reclaimed floor space.
I couldn't remember where i got the idea for this, looking back through my favorites here it appears i got the idea from Dan