Use Opportunities without CRM integration

Hi all,

I've read before that it was possible to use opportunities in Marketo without having a CRM Integration. Has anyone achieved that before? What do you think would be the best way to do this? Ultimately we will connect to MS Dynamics, but it's not in the plans for 2015, so we're looking for a temporary solution that would allow us to leverage that feature along with all the valuable $$$ reporting associated to opportunities.

Thanks for you help.