Using a bundt pan in place of loaf pans
For almost all baking applications, you can freely substitute a bundt pan for a loaf pan, especially for quick breads like banana bread or pumpkin bread.  I have often made my Thanksgiving cornbread in a bundt to get a more attractive presentation.  

You may wish to measure the capacity of your bundt, which is easiest to do by filling it with water to the same level you would batter, and then measuring that.  This will let you compare the volume to your loaf pans.

If you have extra batter after the bundt is filled, you can always make a few muffins to use up any excess.  (Just leave the unused muffin cups empty; it is fine, despite the advise some five to fill them with water.)

Depending on your particular bundt, it may take a little while longer (usually) to bake through than loaf pans will, so make sure you test for doneness instead of relying on timing.

For quick breads, the toothpick test is usually a good one (does a toothpick stuck into the thickest part come out with only a very few slightly moist crumbs on it).



For yeast raised breads, it should also work, although you will definitely want to do your final proofing in the bundt so that the dough can expand into the mold.  You should also use a fairly traditional bundt, not one of the modern ones with many small cavities that the dough might not work its way into.

Again, make sure you are testing for doneness (most yeast raised bread is done around 198 F to 202 F), rather than relying on time.