The OP has commercial software, but for Open Source software (or Cloud-based software built on open source technologies) you should check out my employer.
We are an independent marketing consultancy with 10 members who on average, have over a decade of experience each. We do web marketing, print marketing, community building and management, event planning, strategic consulting and positioning, and anything else you would want out of a marketing team. We can bill hourly or price out a package or campaign.
For startups considering hiring their first marketing employee, we offer a range of specialties and experience for similar cost.
Check us out at http://initmarketing.com/ or email me at Ryan_at_initmarketing.com for more information.
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Ryan Singer