DPM (Data Protection Manager) is more than a simple backup and recovery tool; it also provides continuous data protection. I've trashed DPM 2007 and then praised DPM 2010. DPM 2012 is even better and adds some interesting features as well. For starters, DPM will be able to deploy agents, which makes it fit better in the System Center's management context. The new centralization element lets you manage as many as 100 DPM servers from a single console. That same console allows for role based administration and centralized reporting (something that many have been asking for improvements on). Monitoring is also enabled through Operations Manager.
SCEP (Endpoint Protection), found in the Configuration Manager, provides anti-malware and security capabilities to your endpoint Windows PCs. It works with SCCM to deploy the security client to PCs and the configuration settings for Windows firewall. You may know it better by its old name: FOPE (Forefront Endpoint Protection). FOPE wasn't worth deploying without SCCM because you didn't get all the reporting and alerting elements, so merging FOPE into System Center just makes sense.
SCOM (Operations Manager), years ago called MOM (Microsoft Operations Manager), is primarily a monitoring solution that allows you to snap in various management packs (such as for Exchange 2010). Through SCOM, you can monitor services, devices, and operations through a single console. (That single-console concept is a key aspect of System Center 2012's new approach.) New features include network monitoring (for discovering and monitoring routers, switches, network interfaces, and ports) and application monitoring for Internet Information Services-hosted applications.
Orchestrator is a wholly new component in System Center, though the product has been around for years as Opalis vNext, which Microsoft bought in 2009 and rebranded as Orchestrator. The workflow management tool uses a graphical user interface called Runbook Designer to help automate processes and operations through what are essentially data center scripts.
Service Manager focuses on the user through a more organized way of providing support processes. It lets you track tasks and support tickets via a work log. Its self-service portal lets users help themselves through a knowledge base.