I'm getting comfortable with M$ C# and DirectX. But I love the community and I want to create games that is multiplatform (works on both Linux and Windows).

I am familiar with MS Visual Basic, Basic, C#, Java, (C / C++) and windows programming.

I've never touched Linux-programming before and installed Linux for the first time some weeks ago. Since then I've been wondering "why of why didn't I convert earlier?" Heh, well of course I didn't know Linux was this good...

Well, to the point:

Are there any forums around this topic,
Gameprogramming for Linux
or multiplatform gameprogramming?

I know I need to start learning OpenGL, is OpenGL similar to Direct3D? (Managed Code)

Are there any GOOD books on these topics?

Any other advice?

have a look at opengl.org they have links to tutorials. nehe.gamedev.net is probably the best place to start, although i think it's mainly windows orientated but cone3d.gamedev.net have a few linux specific tutorials.
otherwise ... google

Tnx for the links... if anyone else know any other useful links... let me know

I don't like googling for these kind of tutorials, never find any I think is good enough. It's better to draw some XP from more experienced ppl

Btw: just bought 3 books on these topics... :S well should at least have something to do now...

Yes, there is:

Visit game tome's development forum for the most interesting links: To a Linux game related wiki, how do you do game programming stuff, and the project of the month.

If you're interested in C#, you may also be interested in Irrlicht - a fast 3D grafic engine with .NET bindings. It got a very active forum, and very nice tutorials for beginners. Irrlicht supports Win, and Linux althougth I heard it could need some improvements for Linux. I don't know if it's -NET bindings will run under Mono, though.

Uhm, and I'm not sure if OpenGL is really required to do good games - there are so many mutliplatform grafic engines available: You shouldn't try doing your own.

Have fun.

Tnx... will check it out

Check out SDL here:
libsdl

This is a cross platform low level C library for games. It is a nice API that is very fast. I never got into 3d game development so I am not sure how it does 3d but I know it supports OpenGL. There is a book on the SDL

Programming Linux Games by John Hall from Linux Journal Press. Not a bad book. I would consider some of the information introductory Linux Software Development (covers makefiles).