News Servers:

DHS, Atari.org, atari8.info, Atari Area, comp.sys.atari.st, cs.atari.org, atari.sk
main news servers I check

Nostalgia and Emulation:

Atari Historical Society
best Atari history pages
AtariArchive.com
Countless of Atari XE/XL and ST games. If you're fan of Atari games, check this out!
AtariArchives.org
A lot of old paper magazines/books rewritten into digital form
Computer Magazin Archiv
Similar to the one above, but oriented to german mags
Atari Demoscene 86-97
An archive of the very best classics of ST Demos, oldskool rules!
Steem Engine
If you like old ST games and/or demos but you aren't owner of Atari ST yet, this is all you need!
ARAnyM
Very interesting project, Atari Running on ANY Machine, Atari OS for your PC/SGI/whatever!

Atari links:

Mystic Bytes
The Mystic Bytes and Chosneck homepage, very little updated :)
Satantronic crew
Only active demogroup in Slovakia, Xi is the main organizer of the Atari section of Forever and they are really cool people at all :)
Escape
One of the best Falcon demogroups, but that isn't the main reason why I put them here... Their Hmm... demo saved my Falcon !!! :-) How it's possible? NVRAM in my Falcy was damaged or what the hell it was... So here is certainly the strangest hardware repair story what you could ever read :-) Simply, if you set a TV flag on VGA monitor and reboot, it hasn't any effect. But I did it and Falcon didn't boot to desktop!!! So what now? I had Falcon for about 4 days, it was only 16/32 computer I got that time, I didn't know anything about 680x0 coding and NVRAM... But I "invented" next strange thing: diskdrive worked... if I tried to run some program from /auto folder, it loaded and... after loading there was a silence. BUT. If I tried to move VGA reduction from side to side, magic came here and the program got run !!! (???) Also this was a solution how to run demos. This method had a big drawback: after finishing the demo, it didn't continue to desktop. But Hmm... demo did it !!! No/Escape told me he totally don't understand how it's possible, bcoz all used registers are set to old values... cool, eh? In the desktop I could reset NVRAM and from that time my NVRAM works fine :-)
MiNT List
Mailing list mainly about FreeMiNT kernel and XaAES but you can meet here many professional developers who can answer / discuss nearly any serious Atari-related question. I really recommend to join!
Atari CS List
Mailing list for remaining Atari users in Slovak and Czech Republic. From 8-bit Atari XE/XL to 64-bit Atari Jaguar :)

Coding links:

Ray's 16/32 bit atari page
As far as I know, only Atari site dedicated to Motorola 680x0 coding, really cool!
amycoder's homepage
THE site for 680x0 coding, dedicated to writing optimized code, really nice and useful!
GetBoinged.Org
Cool site with Amiga news, articles, sources, programs... top stuff!
Solo's coders-page
Another Amiga-dude, again Motorola 680x0 oriented
Amiga University
In my opinion, one of the best Amiga sites I've ever seen. This is something I'm still missing for Atari - tons of tutorials, mirrors, news, history, discription of available software/hardware... cool!
Programmer's Heaven
Famous site, but a little bit unclear in my opinion. But you can find nice sources there anyway.
Faqsys
A lot of coding/math tutorials, generally oriented
textfile.com
A lot of tutorials, various topics, from Amiga to BBS manuals :)
flipCode
A damn cool site about 3d/game development, A LOT of useful articles covering nearly all topics about computer graphics

Others:

Hugi Diskmag
Very nice PC mag, not only PC Demoscene inside!
Security Focus
best site about security + bugtraq mailing list
The Great CPU List
Everything you ever want to know about CPUs.. history, technical description, ... EVERYTHING!

Atlantis talker
nema nic spolocne s tymi lamerinami typu pokec.sk
Blackhole
pekny slovensky news server zaoberajuci sa bezpecnostou, PHP, SQL atd
Underground.cz
podobny Blackholu, s dlhsou tradiciou a s namakanymi 'message of the day' :-)
Root.cz
Kvalitny server zaoberajuci sa vecami okolo Linuxu
Krypta.cz
Tiez fajn server, take vikendove citanie okolo kryptografie :)
ABC Linuxu
Server zdrozujuci ludi okolo Linuxu, velmi dobry zdroj riesenia problemov..