I'm not deeply familiar with the NetworkManager CLI, but only a couple of commands are needed.
"nmcli con" shows a list of connections with names and UUIDs. Sample output:
NAME UUID TYPE TIMESTAMP-REAL Auto GloblaSuiteWireless 1aa7870c-0408-4c14-a42a-2e706cabed84 802-11-wireless Tue 28 Jun 2011 12:43:20 PM EDT Auto FLYSBA 37308cf9-b520-4754-b382-8aec39fea79e 802-11-wireless Fri 27 May 2011 11:19:16 PM EDT euca 42696e07-1b3a-49c8-9fd3-4483d9211285 vpn Thu 29 Dec 2011 11:34:19 AM EST
If you travel much, you probably have a huge list of these, so grep is your friend. Once you've found the connection you wish to activate, run this with the appropriate uuid string:
sudo nmcli con up uuid 37308cf9-b520-4754-b382-8aec39fea79e
I've set up script aliases for my favorite connections, so I don't have to search through the list each time. Note that VPN connections can be activated in this way as well.
As always, I hope this little nugget of information saves someone a bit of time someday. It's certainly made my life easier.