The government directly or indirectly sponsors several conferences to promote small business procurement activities with a single or multiple agencies. These can range from free to a nominal fee to very expensive. Avoid the ones that cost more than $100 as you can get great exposure for free and often in your area or within driving distance.
You want to check not only the agency representation i.e. DOD or DOE or NASA or EPA but also who will be in attendance if it is only the small business representatives (officially Office of Small Disadvantage Business Utilization or OSDBU) then do not pay more than $50 or in that range. You should look out for an industry day where a specific agency or location i.e. NASA Kennedy Space Center will host directly or through a small business contractor to have a day where all of their key operations such as Shuttle, Mission Operations or IT will have their key representatives who own the budget in attendance along with the OSDBU representatives aka small business reps.
This is ideal as you can wave the corporate flag and get exposure to decision makers and learn directly about forthcoming opportunities. In your early stages these forums are great as you can also meet other companies and winning is hard to do in this environment going solo but using teams is encouraged and supported by the government.