In my small one man operation, I don't have a sales team nor do I use a dispatching service. I do it all myself, which is easier with the advances in technology. When I started with my own authority, I used a dispatch service who used my load board login and acted on my behalf in finding loads for me as I kept rolling. For the most part, this worked great, but it takes a lot of communication on the front end for that person to know the type of freight, lanes and time schedule you want to work.
After working with the dispatch service for two years, I decided to invest in an iPad with 3G service that gave me internet access almost anywhere while on the road. With that purchase, I was able to part ways with them and start putting the money (9%) from the dispatch service back into my pocket and paid the cost of the iPad off quickly.
Right now, I use two load boards for finding freight. I use Central Dispatch, which is a vehicle transport load board that I've used for years. I also subscribe to Internet Truckstop which I've only belonged to for about 6 months. There's no serious competition for vehicle transport load boards, however, freight boards are very competitive and I had to choose carefully. I signed up for free trials on three load boards and entered the exact search criteria in each one and compared the differences. I chose the freight I was personally looking for and my freight lanes and found that Internet Truckstop consistently listed more loads. That may not be the case for dry van or reefer, but I was searching for flatbed and step deck.
The downside with most freight load boards are that they don't usually list the commodity and freight rate which causes a lot of wasted time calling brokers. Listing freight type with dry van operations isn't as big a deal as with an open deck trailer where freight dimensions come into play. Another downside with freight boards is that you're getting brokered freight; not freight directly from a shipper. This means 10%-20% of the price to move it is taken off the top. Ideally, you want to find your own customers and use the load boards from time to time when your customer's shipping needs have slowed a bit.