What are good online resources for Business Intelligence?

Refer to TDWI site (www.tdwi.org).
It gives you whitepapers, prsentations etc and lot of other useful information

Try first with http://en.wikipedia.org/wiki/Business_intelligence . This will provide you at least a structured background then via google you can pick hundrets of resources based on " business intelligence" search.

It depends on what type of information you want to know about the BI, for me as a technical person; I found these links useful for me: http://www.microsoft.com/en-us/bi/Products/PowerPivot.aspx http://msdn.microsoft.com/en-us/library/aa216365(v=sql.80).aspx#olap:aggregation http://technet.microsoft.com/en-us/library/ms145506.aspx