Well, do you have an account for those providers? If yes, all you need to do is the following:

• Read on python-mechanize
• Download www2sms and have a look at www2sms_providers.py
• Add your own provider class to www2sms_providers.py (take the existing as example, o2online is rather complex because of the additions features, so for the beginning have a look at Vodafon NL)
• Use FireFox Web Developer Plugin to easily get the forms to fill (Or Opera DragonFly)

If you don't have access to those providers, just look out for some public SMS-Service like http://sms.de or any other serious provider you use or found by google: http://www.google.com/search?q=free+sms

Go for one that does not use too much JavaScript, mechanize does not support JavaScript and you have to manually reconstruct what the JavaScript is doing.

Contact me via PM if you want to attend the project or contact me via SKYPE, XMMP. I am glad to help you start.

Thanks for your interest.

Cheers
Bjoern