ERP stands for Enterprise Resource Planning.

Examples:

1. SAP (by the German SAP AG)
2. Oracle's eBusiness Suite
3. PeopleSoft (now also owned by Oracle)
4. IBM's Maximo

Addendum 4/29/2014: Maximo isn't really a full ERP. It is just the asset management piece of the pie. JD Edwards, Lawson, and Workday are other ERPs.