varies greatly depending upon the field of engineering you are in. For civil consulting field we often use the following:
Principal - officer in the company, able to sign and execute contracts, manages a branch, department or office, generally a registered professional engineer in charge of the operation. Appoints a project manager to a project.
Project manager - writes scope of work, negotiates contracts and manages the entire project including the budgeting, client relations, invoicing etc.
project engineer - reports directly to the project manager and is generally in charge of the technical aspects of the project
engineer - one of many who report to the project engineer and do the grunt work, also called staff engineer