For the guys who are hosted here, you'll need a phone and connection able to send MMS.
You'll need to modify your existing MMS settings to send to the server: blogs.dasmirnov.net/mms.php?login=bob&pass=bobpass&cat=786 instead of your usual one, this will obviously mean that a) the MMS will only end up here it won't get sent to the person you specify in the to: line b) normal MMS may or may not work until you restore the original settings. Some phones offer a way to easily switch between two servers.
Obviously replace bob and bobpass with your username and password, cat refers to category, you can either use an existing one or create a new one called moblog for example, your category number can be found by hovering over a link to it.
I've no idea what you'll get charged in theory it should be the cost of an MMS message, however as it's not using your network providers server you may get charged at the GPRS rate.
The default skins only really allow images that are 400 pixels wide, so you might also want to take that into account when you send images.