There are many choices for downloads. One option I like is to do installation over the network. That way, you only need to download the files you need installed instead of everything on a CD. I like Debian GNU/Linux for that. You can download a minimal installation CD of about 150 MB and get the rest from the repositories mirrored all over the web.
Debian has about 25000 packages of software on its mirrors but 1000 to 2000 makes an amazing system. To download their whole repository on CD would be 31 CDs... If you are installing on a lot of machines, you can use tools in Debian to copy the hard drive contents from one machine to another or to cache the downloaded files on a server. Free software means you have lots of choices and you can get whatever you want.
If you have a 64-bit computer than you will want to download the 64-bit version of *nix. But be warned that 64-bit is not well supported, that is you might have problems getting some 64-bit device drivers and programs. I never had problems with the os itself, just device drivers and Abode Flash Player. Ubuntu works better on my 64-bit computer than Fedora 11, easier to install.
can we download linux operating System from internet. if yes then kindly share with me the link.
Almost all of the Linux are free ware and they are available for free except Red hat .There are lot's Linux kernal based os available in market which you have to choose and some of them even use to deliver the CD/DVD for free at you door step.
And as the advocate of Fedora i would suggest you to use Fedora.