Are there any start-ups that specialize in helping other start-ups with their marketing needs? Maybe a start-up running based on a Marketing as a Service (MaaS) model?
I'm a marketing consultant so maybe I can help point you in the right direction, but... Can you specify what kind of needs you have? "Marketing needs" covers a huge swatch of things. If you're looking for a company that "does it all," then really what you're looking for is a boutique marketing agency.
My question was not geared towards a specific business, but I would be interested in online marketing needs. Any suggestions for "boutique marketing agencies" (including yours)?
Sorry, I'm not totally clear on what you're looking for. My specialties are analyzing and optimizing conversion funnels (aka, user acquisition).
There are also startups that solve a specific marketing need. For example, Sverve (http://www.sverve.com) helps you find and work with female bloggers who will promote your content for a fee.
Feel free to mail me at "pushkar (at) inboundio(dot)com" too, will be more than happy to help you