I hate having everything stretched out. Anyone know a way to get games that are in a 4:3 aspect ratio to display black bars on the sides instead of distorting the image to fill a 16:10 monitor?

http://www.widescreengamingforum.com/wiki/index.php/Main_Page
is the first place to go.
after that, your GFX drivers probably have an option to enforce the aspect ratio of lower screen resolutions at fullscreen. with nvidia drivers its called "use nvidia scaling with fixed aspect ratio".
it'll put vertical black bars up at the sides of the game's fullscreen, which may or may not be preferable to you than the stretch.

If you can't find a solution for your game in the Master Game List at the widescreengamingforum, post on the forum and we'll try to find a fix.
If your system will not do fixed aspect scaling correctly (mine does not), another option is to run the game in windowed mode. It won't fill your screen, but the aspect ratio will be correct.

Looos like my ATI card can't do it on my VGA monitor :( I tried windowed mode, but filling only 25% of the screen really kills the immersion. The game is Stonekeep, no listing in WSGF.

Woohoo! Solved it!!
Go to the [render] section of dosbox.conf and change "aspect" to "true"!