Good JDO tutorial ?

I'm trying to learn JDO and am having a tought time getting started.
I'm using Eclipse and have downloaded the Triactive JDO. (It seemed rated pretty well and it's free)
I'm using SQL Server
I'd prefer not to use enhancement because it doesn't sound like the right approach, but I guess I could try it if the tutorial was good

Can someone point me in the right direction? I don't mind trying a different JDO (as long as it is free). But I want to go against sql server.

Chip
.