gx_saurav, go to
http://www.nimblex.net and click on the custom nimblex button. The base distro is 200 MB, and as you add apps you will see the size increasing. After you have finished selecting the apps you want the download link is valid for 24 hours. Nimblex is based on Slackware and very fast. For graphics/monitors which have problems with nimblex, there is an option in the boot menu itself where you can first configure the display and then proceed to boot.
When you boot into the live environment, all you have to do is plug in a pen drive, open the home directory on the desktop, and double clik on the install to usb icon. Its completely wizard driven after that, you don't have to break your head.
There is an option for "persistent", where you can save changes you make in settings to your pendrive.