You keep people for an hour when doing walkaround? :S I've been doing walkaround magic and mentalism for years and never once have I kept people for an hour - If you're booked for say a 2 hour slot, you'll want to move to different groups and people throughout that time, entertaining people in smaller groups to keep the atmosphere up and the room moving while people can still make it to the bar and have conversations between themselves. If the host wanted an hour long show, they'd book you for a stand up performance for that length of time.
Ok, so you're putting together an hour long show... The secret is to build 4x 15 minute sequences and work that way, so look at the over all theme of your show and perhaps you can break it down into 4 pieces and work toward a climax.
I've just put together an hour long show in a similar way which is split into 2x 30 minute halves.
Look at what you want to achieve and the effects will come to you from there, if you're just looking to use other people's material, then check out guys like Ostilind, Maven, Banachek, etc, but I think if you're putting on an hour long show, it should be YOUR show, not someone else's.
Good luck!
DC