It is very, very easy to send a text (SMS) message to an United States mobile number from anywhere in the world, for free. But it is very tricky too. In my desperate attempt to send an SMS to my girlfriend through the Internet, I found a few helpful resources. All of them are free, and MonkeyMaximus is international! If you find more resources, add them as remarks.
Disclaimer: I cannot be and should not be held responsible if using any of these resources resulted in any mobile number being harvested for text spamming.
It supports these cellular carriers: Alltel, AT&T (converted to Cingular), CellularOne, Cingular, Nextel, Omnipoint, Qwest, Sprint, T-Mobile, Verizon, Virgin Mobile
The problem here is that, you need to know the carrier. Don't worry! The next resource is the solution to the problem.
SearchBug People Finder - Landline or Cellular Phone Number?
"Verify if a phone number is a cellular number or a regular (home or office) land line number. The tool also reports telephone company and location. Works for both US and Canada. We use first 7 digits of the number to give you the most precise results on the Web."
Area Code Decoder serves the same purpose, but is also international.
These two resources above may provide false information due to number portability.
Now I faced another problem. I found out that Google SMS does not support US Cellular, which is what my girlfriend has. But luckily I found this page. If you don't have your own number to put as the From number, put one of the To numbers as the From number. I did that with my girlfriend's number, and it worked! (She replies to me as US Cellular has something like SMS-to-email.)
You can send through email, but it did not work for me.
A simple way is to send plain text email to firstname.lastname@example.org (replace the number with your 10 digit phone number).
This will automatically find out the carrier, and forward your message to the appropriate address. If you know the carrier (or find out using the second resource above), then you can send an email directly to these email addresses (where phonenumber is the 10 digit phone number):
Former AT&T customers: email@example.com
Alltel: firstname.lastname@example.org OR email@example.com
Virgin Mobile: firstname.lastname@example.org
AOL's AIM claims to be able to send IM2SMS messages, though this didn't seem to work for me. "In AIM (or any client that you can log in to AIM with, such as GAIM or Trillian), type +(Number) where number is 1(area code)(7 digit number). For example; an IM to +12223334444 would send a text to (222) 333-4444."
Monkeymaximus | TextNation - Free Text SMS Messaging
"Monkeymaximus \ TextNation allows users to send text messages using our website. Users make a custom text message page that they can link to using AIM, Xanga, Blogs, ICQ, YAHOO!, or just ANY place you can put a Link! We also offer a BuddyList feature so that users can have quick access to text messaging their friends. We now allow users to text unregistered users!"
bitBomb.com: Text Message Your Reminders to your Cell Phone
Here you can schedule messages to be sent to a mobile phone (US/Canada) at a specific date and time. You will need to know the carrier.
Free Web SMS : Sanity Software
"I offer a similar free service on my website and support more carriers than Google (including Canada). You can also specify your Sender ID (unlike Google) and send long messages that are automatically split up into multiple pieces."
#1 Cell Phone Prank Site: Play a Joke on Someone - Pranks.biz
Although this site professes to send prank, you can very well use it to send messages that are not prank/joke. "Get at your friends by bombing their cell phones with text messages, i.e. spam. Be creative with your text message (and time of sending) to ensure a most memorable prank :)"