We use SAP BW at work via the server for query analysis. I want to get it installed locally at home to play around with it. Is there a demo version or somewhere I can obtain it?
Its a case of "If you have to ask" But you can start at the sdn download center. And work your way up ( way up ) from there.
Update to comment: Yes its the netweaver thingy. The BW ( or sometimes BI ( its hard to follow sap energetic renaming group)) is part of every "abap stack" for the last few releases. So what you should look for is "NetWeaver abap server" or something like that.
It looks like 'Individual developer licences' are coming soon.
Once you get the BW software, you can ask BASIS questions here http://sapbasis.stackexchange.com/ :-)
Unfortunately, SAP does not give away the BI as a demo version. They only offer the SAP Basis and SAP Java Stack. Both of those stacks are only limited to core basis functionality and don't include any ERP modules. Anyway, without ERP modules and proper ERP data, a BI doesn't make sense at all - you can't really build up a sensible scenario. For such things, I would recommend you to use the IDES scenario, which comes with a full configured business scenario and some bi functionality. There is also a IDES SEM / BI version available.