You might want to consider a "department" strategy.

Structure your service as something that an individual department of a larger company can get hold of without support from IT, approval from on high, or a mess of purchase orders.

37Signals has talked about this in the past, a couple people within a big company start using Basecamp for some one off thing they're working on, then a few more people get added to the project so they get the departmental credit card (used for buying office supplies) and sign up. A few months down the line everyone in the group is using the service.

Yes. Seriously, don't even try. In B2B, you need to make a lot of phone calls, on-site visits, etc. The only way to do this on the side is if you have someone else who is full-time sales. Could be an employee, a co-founder, or a rep. But don't try it by yourself.