Requirements:
You can use http://www.fakemailgenerator.com/
And your going to need a non-premium skype account.
Step 1:
Now, your going to need to go to:
http://www.freegroupvideocallingskype.com/
(yes, it is actually a legit site)
Step 2:
For email enter any email address(it should be working coz u will get ur code in that email only ,u can use fake email generator to generator as many code as u want). You won't get spam, trust me.
Then for skype name, enter in something fake and completely random like: torl123384745ui4 or iofuydhfiudkjfd
Step 3:
Do the CAPTCHA and then check your email. You should get a code in the email which u provided above.
Step 4:
Go to: https://secure.skype.com/account/voucher/redeem (login wid ur real skype username and pass)
Then type in the code.
Step 5:
Login into your account on skype and BOOM! You have unlimited premium.
NOTE:This premium lasts only 7 days, so just rinse and repeat.
just generated 10 vochures..i had used ucweb s60v3 and in email address try any gmail,rediffmail,yahoo,hotmail id and it skype id random98678 anything.and i had not get any error till now.also maybe gmail dot trick working with it.