I have built a 16' boat from plans at Glen-L and I have also built a smaller boat from plans at
www.bateau.com. Both are good companies. I think Bateau has the better plans at this time mostly because the boats have designs similar to anything commercially available. Building these boats is not difficult and no special tools are required. All you need is a work place and time.
I know Oops has a ton of experience, but I have to comment that the stated costs and effort are a bit overstated for these types of plans. I think you are looking at 800 to 1200 hours of work. The costs will be $3000-$6000 plus the cost of an engine and trailer. That said, you can manage the costs yourself. Everything in the marine world can be purchased in a wide range of quality. In the end, the overall quality fo the finished product is completely up to you. It can be a functional work boat or one could go for a yacht quality finish.
I built and used the boat pictured all over Boston Harbor, Cape Cod Bay, Buzzards Bay and Narragansett Bay. I sold it last year and I'm now considering the next build.
Here is a link to Bateau plans from 17 to 20':
http://www.bateau.com/products.php?cat=17
I think the Outboard Skiff 19 and the Classic 19 may be a good fit per your description.
Dan