You could try a few of http://fallout.wikia.com/wiki/Talk:Fallout:_New_Vegas_companions#Returning_Lost_Companions
Also, as the above poster pointed out start dead money and this will also boot any companions you have
Also, you might want to try what's listed in the bugs section on Vault 22
Beware bringing ED-E with you, as it can get stuck in the ceiling, and freeze. However, this problem seems to be isolated to a single room in the 3rd floor "Food Production". In most cases, ED-E can be unstuck by telling it to stop following you, exit the companion menu, and ask it to follow you again.
http://fallout.wikia.com/wiki/Vault_22#Bugs