Did you know that bread actually begins staling almost the minute it comes out of the oven? Yes, you can thank a little chemical process called "starch retrogradation" for this particular effect! However, there is a way that this process can be reversed - at least temporarily...
During baking, starch molecules in the raw bread dough begin to gelatinize at about 150°, meaning they absorb moisture, swell, and then become semi-firm. This is partly what sets the structure (or "crumb") of the final loaf.
When the loaf comes out of the oven and cools to below the gelatinization temperature, the starch molecules reform and harden - starch retrogradation. The water that was absorbed during baking gets slowly expelled and eventually evaporates. Bread that was initially soft and moist becomes progressively harder and dry.
Starch retrogradation can be temporarily reversed by reheating loaves of bread in the oven or individual slices in the toaster. Reheating brings the bread back up to the gelatinization temperature and causes the molecules to reabsorb some moisture. As long as the bread isn't too old or had too much moisture evaporate, this reheating makes the bread palatable again.
The staling process also happens more slowly in breads that are enriched with sugar, eggs, or dairy. The sugar helps to absorb and retain moisture while eggs and dairy both trap moisture and interfere with the retrogradation.
Freezing also prevents bread from staling. Bread can be frozen for several weeks and reheated in the oven with almost no noticeable difference in quality. On the other hand, staling happens very rapidly if bread is stored just above freezing, as in the refrigerator, so be sure to store your daily bread out on the counter!
What do you do with bread that's gone stale?
Related Liking: Bread Bags from UMA
(Image: Flickr member Rene Ehrhardt licensed under Creative Commons)
Soda Recipe: Homemade Ginger Ale
Recipe: Spring Fruit and Nut Tabouli
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
TW Salt Mill by Wil...
The Ultimate Used Furniture Cleaning Kit
Ana Creates a Community at Home
Huh, interesting. This is actually different than we were taught in my food science class about retrogradation.
We were taught that retrogradation occurs when the glucose molecules shift and stack ontop of each other, forming a harder, more crumbly texture. This often occurs when starches are refrigerated, and a prime example is the crumble, hard texture of rice after it's been refrigerated.
This explanation, while different than what I was taught in college, is also very interesting and I'm sure it's another piece of the staling puzzle.
ilovebutter - I don't think our explanations are necessarily mutually exclusive. In fact, I think yours just goes into a little more depth than I was able to in this post. I kinda glossed over the technicalities a bit by saying that "starch molecules reform and harden" - so, thanks!
used up some stale/chewy leftover baguette last night! chopped it up into bite-sized pieces, made a lemon vinaigrette with lots of garlic and some fresh herbs, tossed on the bread to soak for 10 min., then tossed in cherry tomatoes and cubes of cuke for a big, yummy panzanella!
wait, but i store my bread in the fridge, and it's fine...otherwise it gets moldy before I can eat it!
i also store my bread in the fridge. just the regular whole wheat sandwich bread. it definitely keeps it from getting moldy and tastes fine.
as for baguettes and other loaves, you have to eat those quick!