Open Source Systems - open source

Windows opensource and/or freeware

Huge List of Free Software open source
source: above 2 came from the author of OpenOffice guide , reliable ..

______________________________________________________

web based open source systems.- web hosting based

http://www.site5.com/hosting/autoinstaller.php -- these apps must be best systems( and popular ) in their categories like customer support, CMS all web based since these are tested and hosted by site5.
- having this site5 hosting account is the best way to use these apps instead of trying to figure out our own ...

godaddy web hosting account offers these opensource software installed ( similar to site5 above , seems site5 have CMS etc. more )
http://help.godaddy.com/article.php?article_id=17&topic_id=324
http://help.godaddy.com/topic_list.php?topic_id=58



Java and non-java program based ( not web based) open source systems.
So many open source systems, you should not strat from scartch for anything, study these systems you can save 100s of hours. For example in ERP category look at compiere it provides complete code on how to build enterprise java based UI and back end. See Rule engines etc..
Java open source tools/sytems

Java Utilities : Labeled Comma Separated Values (CSV) - com.Ostermiller.util -- this site has many more useful utilities (Excel reader ) , check to save days of java coding ..

For general purpose open source ( not only java but all) see sourceforge.net - The world's largest development and download repository of Open Source code and applications.