http://tldp.org/ : The most usable and master Linux Documentation portal. Nowhere under the sun there is any guide as detailed, as comprehensive and as pure as http://tldp.org . Here you will find howtos, guides, man pages and an online magazine. No hanky panky, only pure information.
http://www.slackware.com/ : Simple is beautiful, that is slackware linux. People use mandriva, pclinuxos, ubuntu, fedora…. to use linux, but they use slackware to master linux. If pclinuxos is the big daddy of desktop linux, slackware is the great grand daddy of everything linux. There is a famous link http://www.slackbook.org/html/book.html , read it to know the ins and outs of linux.
http://www.linux.org/ : The official linux online. It offers applications (source packages), information on distributions and downloads to famous linux, books and all. You will get real big linux news here.
http://distrowatch.com/ : All about linux distributions, their rankings, updates, releases, news and all that. The best resource for linux hobbyists.
Not Linux related but interesting anyway
http://www.firsteuropa.com : As you can not do without a car, you can not ignore car insurance. So, why not book your insurance at First Europa and save big money? First Europa is a leading insurance brokerage in Europe. It is growing to spread across the globe like wildfire. Next time you think of buying an insurance visit first europa to save big money on your insurance policy.
http://www.alistapart.com/ : The veteran website on content, design and e-marketing. As they say - “from pixels to prose, coding to content.” It has them all. Besides, those designing, content and marketing, if you wish to hone your writing skills, just read a few article at
http://www.thebrandsmith.blogspot.com/: My friend Amit's personal Blog! Quite often he stuns me with his witty remarks and creative sparks. I am sure this blog is going to be the big daddy to compel designers to spell their words about brand, business... and designing.
http://www.contentwriterindia.com/: Those who are looking for "content that really works" should visit this website by Ritesh Tanu, my one time fellow content writer. I know him for long for his die-hard attitude towards perfection. Also he happens to be an avid Linux supporter.