For sending free SMS you have to sign up for an account and every time you have login. Some users dont like this so they want to send free SMS without opening an account.Here is some services that let you send free SMS without login or signup.

I found three sites, More sites added soon.

(1) wapvilla.com

Here I am posting site which provides free unlimited sms with Some Cool Features. like..
-No Character Limit 

-No Advertisement

-No Login Required

-Fast Delivery

-Annoymus Sms

-Send Now

2) BollywoodMotion
This site let you send long SMS, and it is the only website that let you send maximum characters (500) in SMS.  All you can do without login but you need capcha.

(3) SeaSMS
SeaSMS let you send MMS in India but you can send SMS too. without login. It does not ask capcha that is a very nice thing. You can compose SMS in Hindi language.