Configure your XF86Config file to have multiple resolutions like say:
Code:
Section "Screen"
Identifier "Screen 1"
Device "** Intel i810 (generic) [i810]"
Monitor "My Monitor"
DefaultDepth 16
Subsection "Display"
Depth 8
Modes "1280x1024" "1024x768" "800x600" "640x480"
ViewPort 0 0
EndSubsection
Subsection "Display"
Depth 16
Modes "1280x1024" "1024x768" "800x600" "640x480"
ViewPort 0 0
EndSubsection
Notice the multiple resolutions for my different depth settings, with that in place you can just simply do a
ctrl - alt - ( + or - ) to change between resolutions.