Backup alternatives

I am curious to know if anyone has any viable live backup procedures other 
than pg_dump/pg_dumpall when you have a continuously running server with 
continuous query activity?  The motivation is to find a live alternative 
faster than pg_dump, which presently takes about 45 minutes on some of my 
larger databases.  I assume any kind of file copy backup is not workable 
due to the complexities of mvcc, caching, etc.

Thanks,
Ed