We have a bunch of Microsofties at YC today, but reach out to Steve or me directly at (founders@microsoft.com) if you're a Winter 2015 batch company and for some reason not at YC today.
It's also worth pointing out that our $60k offer for YC companies is still around, if you're in one of the older batches.
Not a YC company, but we'd love to buy you and Scott coffee or lunch if you're free tomorrow. We (Fanout) received a boat-load of Azure credits that haven't been used, but with all of the cool new Microsoft OSS developments recently we think it'd be great to start working on Azure. My twitter/phone# is the same as my HN handle.
It's also worth pointing out that our $60k offer for YC companies is still around, if you're in one of the older batches.