I've noticed a lot of Twitter-related posts on DCP lately. So, lets get a comprehensive list together of corps/members who are posting from tour, along with their screennames.
DCI World Class
Pioneer: @PioneerDrmCorps
Boston Crusaders: @bostoncrusaders
Madison Scouts: @madisoncorps
Cavaliers: @TheCavaliers (also @marimba06, head DM)
Phantom Regiment: @PhantomRegiment
Holy Name Cadets: @TheCadets
Colts: @TheColts
Spirit: @SpiritDrumCorps
Crossmen: @Crossmen
DCI Open Class
DCA Open Class
Music City Legend: @MusicCityLegend
Caballeros: @Caballeros1946
Bushwackers: @BushwackersDBC
Buccaneers: @RdgBuccaneers
DCA Class A
These are the only ones I have right now, but I'm new to Twitter. Let's see how many corps are on Twitter!