JAVA

 ABAP developer needs to gain different skills for better understanding of abap beside the other benefits. If you agree and still haven't decided where to start , you should take a look at JAVA. It is probably the most powerful language.

  Using JCO (Java connector) , you can directly call remote enabled functions. Sap Netweaver Developer Studio (NWDS) is the provided ide to develop java applications integrated with sap. You can download JCO and NWDS from SAP marketplace. There is also a book published by SAP Press to begin programming with java.

ABAP vs JAVA : http://enterprisegeeks.com/blog/2009/03/23/egeeks-podcast-episode-12/

Java Beginners : http://download.oracle.com/javase/tutorial/index.html

Netbeans IDE: http://netbeans.org/

JCO : http://help.sap.com/saphelp_nw04/helpdata/en/6f/1bd5c6a85b11d6b28500508b5d5211/frameset.htm

WDFJ : http://help.sap.com/saphelp_tm60/helpdata/en/15/0d4f21c17c8044af4868130e9fea07/content.htm