As a few social networking heavyweights seize control of the majority of market share, there’s still money to be made filling in the gaps, through clever applications that round out the site experience or for tying several together into one convenient tool. Seesmic is positioning to cover both these fronts by buying ping.fm, one of the more popular tools for updating multiple social networking sites. If they can successfully merge the two programs into one dynamic product, they could actually outlast the services and grow as an extremely useful Tweeting tool.