The book I read to research this post was Mobile Marketing For Dummies by Michael Becker et al which is a very good book which I read at
http://safaribooksonline.com
This book is a few years old so some of the technology in it might have been superceded like at the time of publication Windows Phone 7 hadn't been released yet. Apparently in developing countries almost everyone who can afford it has a mobile phone because the infrastructure of a standard phone network just isn't there. This book is about marketing your company for people with mobile phones and a lot of it's geared towards the smartphone market. A lot of companies get a mobile marketing agency like www.constantcontact.com. An interesting technology is IVR or Interactive Voice Response where a customer phones you and is presented with a menu where they press a button or speak into the phone to activate an option an example is www.angel.com of a provider. Some banks like Western Union are allowing people to buy stuff direct from their mobile phone an interesting example is Amazon where you simply enter your password and your credit card details are entered automatically once set up initially. If you get a mobile website I have one at http://oldescratbag.com a good provider which I use is weebly or try
http://starcut.com .Some companies use a bluecast provider at shows or exhibitions etc where a message or photo etc is sent to people walking by your stand by bluetooth and they have the option of accepting it or not. An example is
www.aura.net . Also a website I recommend which is all the latest mobile technology news is http://engadgetmobile.com . I enjoyed this book and it has a lot of information about mobile marketing crammed into it.