For example, the Inventory Open Interface (IOI) was designed to provide the ability to load large numbers or batches of inventory items at regular intervals. If you have 2,000 or more items, or regularly add 100 or more items at a time, you may want to consider it.
Similarly, the Applications Desktop Interface (ADI) can be used to load journal entries from Excel or other feeder applications into GL.
For assets, you may wish to use the Mass Additions Interface in Fixed Assets.
In general, the open interfaces allow you to add data to specific tables, usually via Sql*Loader, then run an interface that performs some level of validation of the data, then loads the applications' tables appropriately.
Oracle has a new product/utility called iSetup which is designed to help install Oracle applications. Its "Chart of Accounts Companion" allows users to define segment values (up to 9) in a spreadsheet and import the values through the loader.
DataLoader -- program from Comstar at http://www.dataload.net/. It uses Excel macros and Oracle forms. Use the link to download the dataloader program and commands.