Can someone who has left US for good (and doesn't intend to return) claim the SSN and medicare taxes that have been paid during their working years in the US on H1/L1 VISA? And which are reported by Social Security Administration on a annual statement. Specifically for my case, I had 24 credits as of the last statement at the time of leaving US.

SSN or SSI?

No, you will not get it back.
Read about L1/H1-B taxes: Your U.S. Tax Return: The U.S. Visas (http://taxipay.blogspot.com/2008/08/us-visas.html)

Jason:

What MukatA says is true! You have no option for claiming a refund for FICA taxes paid while under a H-1 or L-1 visa.

However, if your home country has a totalization agreement with the U.S. you will get credit for those FICA payments on the equivalent programs within your hoem country.