Notices

Is there some app that will open .dwg files, or if you don't know, AutoCad files. I don't mean editing, just viewing.

Highly doubtful... but surely creating an app to view the DWF version shouldn't be too hard...

Unfortunately, while DXF is decently well supported under desktop Linux, to my knowledge, there is no currently-maintained Linux program to directly view or edit DWG. There is a reason for that, but I can't recall it off the top of my head. I ran into that issue when I downloaded the plans for my university, and ended up running a shareware converter in Wine, which was rather painful with that volume of files. If you can prove me wrong, I'd be happy, but I don't think you'll have much luck. Would it be practical for you to convert them once to, say, vector PDF, or is this an ongoing thing?

I tried some programs that converts .dwg file to .pdf, but the result was nothing good. Can you recommend some good program for that? Some program that will make pdf almost the same as dwg, i mean black background, line colors, and most important, to don't blur the image. By blur i mean when i zoom in, lines become weird.

Ah, it sounds like what you were using is rasterizing the DWG, even though PDF supports vector natively. To be honest, I can't remember what I used, and it was a really lousy demo version of a lousy Windows app that probably cost about $20-30. I'll see if I can find it again after I eat some lunch, but no promises. It wasn't a good solution, but it worked in a pinch. If I may ask, what is it that you need to view on the N900?

DWF is AutoDesk's web-specific file format. I once wrote a Windows viewer/manager for these files.

There's some promising info on this wiki page:

http://en.wikipedia.org/wiki/Design_Web_Format

Print a pdf with Adobe out of AutoCAD (you only need to create a pen setting that will reflect your screen rather than black on white....
But I would love to have a dwg viewer as well. I seem to remember that there used to be on on symbian (I know it's not maemo....)

Sure, but it's not me who actually need it. My dad also has N900 and he need some program that will open autocad files.

What about Blender? http://www.blender3darchitect.com/20...ing-dwg-files/
Blender runs in Easy Debian, so there is only the 3d-driver problem left...

Yeah, I did a quick look into things, and the situation isn't good. To start with, the first relevant Google result for the query "dwg linux" is a program based on Qt2 (ancient history, if you're not familiar with it), and I'm not sure if that's even available anymore (edit: "that" being the program, not Qt2). From the Wikipedia page, it looks like Autodesk has been patent/trademark-trolling anyone who does anything to do with DWG for years. Here are some highlights (bad word choice, I know ):
The article does mention that the FSF has been working on library support for DWG (and probably doing a campaign of snarky slogans and stickers :P), which was partially functional at the time of writing. GNU Savannah page is here. Apparently it's written in C and... Esperento?!... Alrighty-then. I guess I'm not going to be reading the source. :P This is on the FSF's "high-priority FOSS replacement" list, so hopefully it will go somewhere useful. For the moment, though, I think you're out of luck unless you can convert it to a more open format.