Want to test out BES? Have a few users you need to mobilize? Need to do a proof of concept? If so then RIM have a good deal for you, a free BlackBerry Enterprise Server for IBM Lotus Domino. The Quick Start edition is good for up to 10 users for no cost, and 15 for a small fee. See the BlackBerry site for more info.
For assistance, planning or licenses (once you need more than 10 users) contact STS, your BlackBerry Alliance Member and IBM Advance Business Partner.