PostBooks (http://www.xtuple.org/ http://www.xtuple.org/) is a fairly capable replacement for Quickbooks on OSX (and Win/*NIX), and has both OSS and Commercial

PostBooks (http://www.xtuple.org/ http://www.xtuple.org/) is a fairly capable replacement for Quickbooks on OSX (and Win/*NIX), and has both OSS and Commercial versions. GnuCash (http://www.gnucash.org/ http://www.gnucash.org/) is another I've used in the past and had good results with. It's more of a Quicken replacement than QuickBooks though.