David Davies has set up a moblogging guide:
Mobile blogging is easy. Don’t let anyone tell you different. All you need is a mobile device such as a mobile phone or a wireless lap/palm top. In fact it doesn’t matter what hardware you’ve got as the important thing is it must be able to send an email message. Most mobile phone service providers will either let you send an email directly from your phone or they’ll operate an SMS > email gateway where you send an SMS message to a special access number that in turn routes your message out to email.
He covers the basics well, though if you want to add pictures to the mix, you should take a look at Manywhere Moblogger for pictures and text.