in general, most programs should be designed to resize gracefully to some minimal size, like 800x600.
different gui libraries have different facilities for doing this.
for example, if you use delphi or c++ builder, you can set "anchors" on most of your controls which control the way the resize.
i am a big fan of non-fixed-sizes applications that can be resized. some programs like winamp, are skinned and are not meant to be resized.
ps. this should be in developers section, so im moving it there.