Virgin Mobile, and Twitter?

[Pager Salesman]

As long as you have an unlimited, free text option for your plan, you're all good. This doesn't cost extra unless text isn't included in your plan

In my situation, I have 50 texts per month, so I limit my texting to that number, but I still update my Twitter statuses every now and then from my phone.

How to set it up:
From your Twitter profile, or any page, go to Settings.
Select the Devices tab
And enter in your provider and phone number.
You may have to send a confirmation code in order for you to start updating from your phone.
Once that's done, text all your updates to 21212; you may also subscribe to updates from your friends or other people you follow!

Example:
To: 21212;
Message: Just finished getting a haircut, on my way home!