How does everyone send these? Regular envelopes? I wouldn't want them to get messed up, though, going through the machines and stuff.....
For me it depends on what's on the card. If it has something breakable on it, I (generally) try to wrap it in bubble wrap. I put all my ATC's in snack size ziplock bags ('cause I'm ghetto like that). Soon I'll break down and but some actually ATC card protectors.
For my cards I've been using old board game cards (A game called Mastermind). The cards are the perfect 3.5" height, and they are long so I can get two out of one.
MichellesCraftBasket, if you get bored, you could always premake some ATCs for some common themes and then they will be ready to go when you get the opportunity to claim someone w/ that theme. We all had talked about this a while ago. Such smarties on here!