RAGBRAI is fun! And the pace can be relaxed or fast or anything in between. Lots of opportunities to stop for food, so just the regular fixit things (like on the what's in your saddlebag thread) and some money. It's just one giant group ride. We ended up riding with people sometimes, I guess it's that natural group together thing, so don't be surprised if you end up in a group of like speeded peoples.

It's a 71.1 mile day. If you can do 50 you can prep yourself for this just fine, both knowing how to fix a flat if you don't already and getting some ride time in. If you have group rides in your town it's a good supported way to get used to riding with groups of people. Basically it's like motor traffic, slow traffic to the right, obey traffic laws. Mostly, have a great time and if it's freaking you out, stop reading that message board!