I have Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c) and when I plug a vga or HDMI cable I can't see the second monitor and the I only see a mess main monitor, like this screenshot http://ubuntuone.com/p/rBo/.
I often use a second monitor with my laptop, which has an Intel GM965 video card. Usually it works fine, sometimes it fails in one of the two ways:
VGA hotplug detection works for me in 11.04 (it didn't in 10.10 or earlier versions), so it's enough for me to plug in a monitor and wait about a second for it to be autoconfigured. If this doesn't happen for you, or if Ubuntu's chosen autoconfiguration (cloned display versus extended desktop) is not to your liking, you can run
I don't have a HDMI connection on my laptop, so I cannot say from personal experience if there are any bugs affecting HDMI.