Index rebuild online is only available in Enterprise Edition

http://msdn.microsoft.com/en-us/library/cc645993.aspx

Online does not mean it does not lock. It is "almost online".

Rule of thumb:

5%-30% fragmentation - use reorg

30%-100% fragmentation - use rebuild

you can run an Agent job with two steps.

reorg uses 8K page to rewrite index one page at a time with no rollback.

rebuild completely recreate the index and switch over.

I have a newer version that resets fillfactor along the way if fillfactor=0. It is on SQL Saturday #308 recording on my web site.

From SQL2012 later, index included LOB column is allowed rebuild online.