One of the new features of Project 2007 is a new type of resource called a Cost resource. Previously there was Work and Material resources. The Cost resource adds the ability account for costs on tasks that have no relationship to the Work assigned on the task.
You might be saying to yourself that Project already had a feature that allowed you to do this called Task Fixed Cost and that this feature has been around since Project 98 (or was it Project 4? I can't remember.) If you are saying this you are right. However, Fixed Cost only lets you account for one 'lump sum' of this kind of cost per task. It was not very good for situations where you had more than one kind of cost per task. Cost resources make it easy to have multiple non-work related costs on a task and keep track of them easily. Even better they allow you to keep track the amount of each kind of cost across all the tasks. For example, if you have two Cost Resources, Travel and Hardware you can assign them to many tasks and then using the Resource Usage view you can see quickly how much money is scheduled to be spent on Travel and Hardware across all your tasks. You can even use the Resource Usage view to adjust where across the duration of the task the cost associated with the cost resource falls.
Assigning costs to a cost resource is done the same way as Units are set for an assignment. In the Assign Resources dialog there is a new field called "Cost". It is only active for cost resources. When you assign a resource to a task you just enter the amount you want to represent for that cost resource and click 'Assign'.
This is pretty cool stuff!