SMS touch for iPhone and iPod touch is available now in the App Store.

SMS touch includes 10 SMS text messages.
If you register the app with your SMS Mac account ID, you can use your current SMS balance and you’ll will receive 10 extra SMS. So, in total, 20 SMS will be added to your SMS [...]

Version 2.5.1 of the SMS Mac Address Book plug-in is available for Snow Leopard. SMS Mac is the Address Book plug-in to send SMS text messages.
Added feature:
Reply to Email support in USA and Canada
Compatibility with Snow Leopard.
You can download SMS Mac 2.5.1 here:
http://www.smsmac.com/download/SMSMac251.dmg
Requirements: Mac OS X 10.4 and up (including Snow Leopard).

Available for download is Send SMS 2.4, a new version of the Mac OS X Dashboard Widget to easily send an SMS.
User feedback for USA destinations has been improved in the case of features like Unicode SMS, Long SMS and Reply to Email.
Secondly, the widget now also supports the sequence 011 as a international prefix.

You [...]

Version 2.5p of the SMS Mac Address Book plug-in is available for Snow Leopard. SMS Mac is the Address Book plug-in to send SMS text messages.
Added feature:
Compatibility with Snow Leopard.
You can download SMS Mac 2.5p here:
http://www.smsmac.com/download/SMSMac25.dmg
Requirements: Mac OS X 10.4 and up (including Snow Leopard).

Version 2.5a of the SMS Mac Address Book plug-in is available for Snow Leopard. SMS Mac is the Address Book plug-in to send SMS text messages.
Added feature:
Compatibility with Snow Leopard.
NB: The Group SMS plug-in is not yet compatible with Snow Leopard. For the time being, you can send a Group SMS with the Send SMS [...]

Version 2.4 of the SMS Mac Address Book plug-in is available. SMS Mac is the Address Book plug-in to send SMS text messages.
Added feature:
For most destinations in the Caribbean you can now use Long SMS and Unicode SMS.
Improvements:
Improved alert when your SMS balance is not sufficient for Group SMS.
Improved alert for slow SMS Mac server [...]

Available for download is SMS Mac Scripting Application 2.2.

Version 2.2 now also supports the Reply to Email feature of SMS Mac.
Reply to Email means that SMS replies will be delivered to your email address instead of to your mobile.
You can now use code like:

set sender to “john.doe@mac.com”

We have extensive documentation about the SMS Mac Scripting [...]

Available for download is Send SMS 2.3, a new version of the Mac OS X Dashboard Widget to easily send an SMS.
We improved two important features:
Regarding the Group SMS feature, the widget gives more feedback about which mobile numbers in the group were actually not sent (because of mistakes in the mobile numbers). Also, we [...]

Version 2.3 of the SMS Mac Address Book plug-in is available.

We improved the Group SMS feature of the plug-in:
The SMS Mac Address Book plug-in now gives you more feedback
about which mobile numbers in the group were actually not sent
(because of mistakes in the mobile numbers). Also, SMS Mac will always
immediately submit the Group SMS to [...]

Version 2.2 of the SMS Mac Address Book plug-in is available.

New users who want to check out SMS Mac can now request a trial SMS Mac account with 3 free SMS text messages. You can request a trial account through this web page:

Free Trial SMS Mac account

The [...]