ETL means extract transform load. During your identity and access management implementation the information for the users might come from different sources and to consolidate into a common place you can use any ETL tool.

Usually is required on you identity system to prepare your users for initial load into the system.

Some tools you can use for that are:

CloverETL (http://www.cloveretl.com/)
CloverETL is open source data integration platform based on Java. It can be used for data migration, data cleansing and other data transformation tasks.

JasperETL (http://community.jaspersoft.com/project/jaspersoft-etl)
Jaspersoft ETL is a data integration platform providing high performance data extract-transform-load (ETL) capabilities.Jaspersoft ETL is easy to deploy and out-performs many proprietary and open source ETL systems.

ScriptellaETL (http://scriptella.javaforge.com)

Open source ETL (Extract-Transform-Load) and script execution tool with support for JDBC/ODBC, CSV, LDAP and XML data sources.

Take a look on the next wiki link to read more about ETL process http://en.wikipedia.org/wiki/Extract,_transform,_load