Two wireless usb nics
 

Is it possible to have an internet connection and share it to other computers through another wlan hardware? Possibly the second one needs to be set up as an adhoc network. How could I accomplish this?

Most distros will allow you to set up two nics.
Some nics can be set up to act an a WAP, which can be handy. Ubuntu and CentOS from your list - though I've only seen it happen in Ubuntu 8.04.

You set it up in IPTables just like for any dual-homed-host.
Search these forums - there are many threads on the subject - doing this with wires.
Wireless is much the same using iwconfig instead of ifconfig. IPTables is identical, but for the interface names.