What exactly are you trying to accomplish? Are you trying to build the community and engage the existing users? I'm going to assume both is true. But the first thing you need to ask yourself is what are your goals with the community. Then ask yourself what tone do you want to set for it? Start by reviewing the communities of similar sites in your market. Some great examples would be the 37 Signals and Zappos communities. Balsamiq also has a great community too. All of them share a common trait: There is a personable approach in their writing and sharing.

A few things: Instead of asking for PR at blogs, offer to guest blog at those places. It opens your company to a broader audience. Make sure to follow up on every single comment too. Then offer other companies' community managers to guest blog on your site. They will make sure to tweet/FB their posts to their audiences and it starts a reciprocal relationship.

Email is underrated. Yeah, I know people think its dead but we send out an email each week and highlight product developments, share articles relevant to our users, and highlight our blog posts. We have a very high open/click-through rate and see an increase in Twitter chatter for about 3 days post-mail.

Next, highlight your users: show the community how people are using your site/product/widget and ask your community to guest blog for you. Highlight your users in your weekly emails and tweet out their stories/contributions.

Have webinars or twitter chats that scheduled and have a unique hashtag. They don't have to be directly related to your product but a general discussion about the industry. Reach out to businesses in your field and ask them to co-host these with you in a roundtable fashion or Q&A setting.

The above should get you started and spark more ideas along the way. And the best part is you can do all of these at no cost except the time you spend. Good luck!

Clearly define what your aim is (not "grow the twitter followers by 50%") in a business context. "I am going to build a relationship with 50 bloggers pertinent to our product"

Your community is likely to be very nascent, and so you'll need to complete grok the space your in, really take the time to understand what the "continual conversations" are between the community (there's always one. Think Python vs Ruby on HN)make sure you understand it, the key players who takes which view...

Once you've fully groked the environment, use being the "twiter dude" as a way to meet people for coffee's and beers, then scale to being a biz dev.

Simples.

Remember, you there to make money not have a natter. :)

I recommend you attend Meetup events relevant to your field- meet the organizers and the attendees, find out what's important to them. If your startup has their own space, talk to the organizers and offer to host a future Meetup at your location (throwing in free beer and or pizza always helps sweeten the deal ;) ) or ask if you can present your product to the group at a future event.

In regards to having our own space we do not as of the moment. But we anticipate that time coming soon and this is a great idea, writing this one down now. Thanks for the idea!