OOP concepts : resources?

the more I read about "real" programming, the more I realize how little I know. I can script in Flash 5 pretty good, building dynamic systems that populate objects from data (for example, complex menu systems that have only one re-used label object).

I feel like I have hit a wall, and the next step in learning true OOP seems big to me. I read about classes and components, and creating my own objects... but I am getting confused. I know what I am working on could be much more efficient if I could intelligently apply basic OO principles. So far I have been coasting on common sense.

Is there a resource out there that gives a solid language-independent explanation of these concepts? Even simple Java (or something similar to ActionScript syntax) source that is legible would be welcome. Not really "programming for dummies", but a more intermediate-level?

thanks,
tim