I) So here's a cool, but fairly complicated one:
a water-proof solar charger that you can use for, e.g., charging your cell phone.
What makes it cool?
1. It's water-proof.
2. It connects to two AAA batteries, which means -- you can let the batteries charge all day, and then hook up your cell phone to charge at night. Just like a regular charger!
... This is as opposed to an "emergency" solar charger that you might carry on a hiking trip, and you'd have to leave your cell phone hooked directly up to it for a full day or more. Vs with this one, you can just charge the batteries.
3. Oh, in fact, it could even just function as a battery charger. Apparently it's fairly simple to substitute other battery types (like AA) instead. Have a digital camera that runs off them?
4. It will save you (a little) money!
II) These look like cheap metal racks that might be used in an oven, maybe? or something -- but cheap metal racks that get thrown away or sold for a buck.
Very easy, affordable way to make hanging (non-mounted) and adjustable shelves, if you need something cheap and can't mount something but you do have something to hang them by.
... The title pretty much says it all.
Not much in the way of explicit instructions, unfortunately; but what he does write, plus the pictures, are enough that I think I could put one together. It *would* be useful (though I don't know if it would fit in my current space).
IV) Another not-real-explicit project, but again, the pictures + some text seem that they'd be enough: http://www.instructables.com/id/25_Rack_stores_five_bicycles/
V) YES. This is just the sort of thing I've been brainstorming myself, thinking about ways to get my clothes organized (with minimum sustained effort, of course). It's larger than it should be for my needs, so I'd probably just adapt it to be smaller.