I've been doing a lot of yeast bread baking as of late and I got to wondering what the salt in the bread was for.  Upon doing some research it turns out (aside from perhaps some flavor) the purpose is to "Control" the yeast during the rise.  This got me to wondering if it was possible to make a yeast bread with no salt at all.  My first attempt was met with defeat, and upon some more experimentation I was able to get the salt down 75% with success.  Its the last 25% that alludes me.  Is it possible to make a yeast bread with no salt? 
If you make a bread without salt, you will have to make the dough dryer as well. Salt (for lack of a better word) competes with gluten and yeast for moisture. Without the salt, the yeast will work a bit faster (this effect isn't that pronounced) and the gluten will be very soft. The effect on the gluten usually causes loaves without salt to fall flat as the gluten is overly extensible but not very elastic. This could be part of why your loaves are collapsing, as without salt it is very hard to maintain the tension of the outer gluten sheath.  As SAJ14SAJ points out, the lack of salt will make the bread taste very "flat". While there are breads traditionally made without salt, they are usually served with very flavorful accompaniments like olives and sardines. Depending on what you're using the bread for, I'd suggest using an enriched dough as the added flavor of eggs, butter, and/or sugar will also help to cover the lack of salt.   Edited to add links to a couple of articles describing salt's effects on dough and one on salt taste in general. 