Alternatives to Google SMS

Ipipi.com
Ipipi.com is a service that offers global SMS as a subscription. At the time of publication, ipipi.com provides global text messaging for 10 cents per text, or plans with unlimited incoming and 1,000 outgoing texts for $85 per month. The key element is that ipipi.com is global, which separates it from other services that only provide national coverage.
TextSendr
TextSendr is an online messaging service that allows for SMS messaging through your browser without an account. All you have to do is type in the recipient's phone number, and the message is sent. By entering your email address, replies to the text messages are automatically sent to your email inbox, where you can continue the conversation through email. The only drawback with TextSendr is that it requires the recipient to have picture messaging enabled. Otherwise, SMS messages never arrive.
Text'em
Text'em (textem.net) is a simple text messaging portal that allows for messaging online. Like TextSendr, picture messaging has to be enabled on the recipient's phone. Unlike TextSendr, you can create a free account where you send and receive text messages through a chat-like interface.
MySMS
MySMS is an app that installs to your Android SMART phone or device. Once installed, you can send and receive texts through the app or by logging into your account on your computer. There is no way to use the application unless it is already downloaded and installed to your Android device.
Yahoo!
Yahoo's email service provides SMS text messaging in much the same way as Google. All you have to do is add the phone number to the contact information in your 'Contacts' and click on the number once it is saved. A chat window will open and you can enter a text message just as if you were chatting with the recipient online.