I've tried the ClimbTech 1/4" and 3/8" removable bolts, that are no longer available, but I didn't feel real confident on them. As you probably already know they're a type of spring loaded slider nut designed to be cylindrical so that they fit in a hole, but since they go inside the hole it's hard to inspect them to see how well they're seated. The only way to determine the quality of the placement is to bounce test them. Then you need a custom tool to remove them. James Hunter and Larry Shaffer must have most of the world's supply, and they claim they're good for catching leader falls, but I'm not so sure. You can get by with a slightly shallower hole than you would drill for a wedge bolt, but then all the bounce testing and extra time to clean them means they aren't all that much more efficient (at least in my limited experience). These have been used a lot in recent years in Lech where hand drilling is necessary.
If you want a removable bolt and you can power drill, then the Fixe Triplex 12mm x 55mm is a good choice. I used these in Hellhole a little while back. The hole is a larger diameter than the more standard 3/8", but the shorter length of these bolts means about the same amount of rock removal and battery depletion per placement. For temporary removable placements I use the larger diameter bolt hanger (12mm) and place the hanger under the lip of the sleeve. This makes them easier to clean because you can yank and pry the hanger to get the bolt out. I put a 3/8" o-ring around the base of the hanger to keep from losing the bolt during cleaning. For long-term placements I use the smaller 10mm hangers and put them on top of the sleeve collar. If I'm placing them during an aid climb and then immediately cleaning them, I don't even bother to clean the holes.
If you can power drill, and the main reason for wanting removable bolts is to mitigate the cost of leaving a bolt every 3 feet, then consider using non-removable steel wedge bolts. You can buy these in bulk for around $0.30 each so a 100' dome climb means you only have to sacrifice $10 in hardware. The hangers of course can be recycled. The small stud that is left behind isn't very noticeable and isn't going to cause any significant environmental impact.
Other options include rivets (threaded hex head bolts hammered into a hole), or concrete screws. I haven't really used these on aid climbs, but I've experimented a little. The Tapcon 1/4" x 1 1/4" hex head concrete screws might make a good quick body-weight placement. These appear to be similar to the link Martin posted above. I believe they are rated to hold 400 lbs so you don't want to bounce test too vigorously. I have a bunch of butterfly rivet hangers that can be used with these. The hole is only 3/16" diameter and just over 1" deep, so for hand-drilling there's significantly less effort, and they go into rock amazingly easily.
http://www.concretescrews.com/http://classic.mountaingear.com/pages/product/product.asp/imanf/Yates+Gear/idesc/Butterfly+Rivet+Hanger/Store/MG/item/215440/N/1045%204294967263