Yes, the Oregon 600 can use routable opensource maps (see the Maps page here).
They are new and more expensive, but the Oregon 7x0 series have direct (via wi-fi or bluetooth smartphone) access to Geocaching.com data, so no need to connect to a computer if you don't want to!
Thank You Atlas Cached! After dropping my phone in the lake hunting for a boating GC last week, I've been on the hunt for a waterproof gps. It's worth it to me to spend a little money on a unit that will make this hobby more enjoyable. Boy would I ever love to have that 700 and not have to use my computer at all. I see I can buy a used one for $319 ...hummmm might have to go for that one. Thanks again.