Question: I am using magento community version 1.8.1. I am using FedEx for shipping method.

I enabled several method like 'First Overnight','2 Day','Priority Overnight','Standard Overnight','Ground' and 'International Ground' from admin.

But only four are appearing in front end. 'Ground' and 'International Ground' is not appearing.

Can anyone help me on this ?

Answer: 
I had a similar problem, but mine wasn't related to 'Residential' being set or not - international address post-codes weren't passing validation.  

USPS ignored this, but FedEx's API did not. 

This issue could be one of many issues and as Magento allows shipping methods to fail silently - I suggest enabling "Debug" for the shipping method, and checking in var/log/shipping\_fedex.log and look in the "result" Object.
What packaging type have you set in the admin (System->Configuration->Sales->Shipping Methods->FedEx->Packaging)? I think for FEDEX\_GROUND you need to set the packaging to 'Your Package'.

But I am not certain of this. The available shipping methods returned by the FedEx API remain an enigma. Try lots of different settings and see what types are returned. Maybe FedEx help desk can tell you the magic settings you need to pass into the API to get FEDEX\_GROUND back.

If you want to dive into the code, read `/app/code/core/Mage/Usa/Model/Shipping/Carrier/Fedex.php`.