The absolute closest business type hotels to the Convention Center are the Peabody, Rosen Plaza, and Rosen Centre (they often seem to use that area for overflow parking as well). Check out this link
http://www.occc.net/pdf/Map_Web.pdf to see all of the hotels in the immediate area.
That being said, every year when my company attends an expo in the spring time we stay at the StayBridge Suites on I-Drive (walking distance to Pointe Orlando). This is a business traveler oriented hotel with good rates. All rooms have a separate (door between) living room and bedroom as well as a kitchen area (with fridge/stove). They have a continental breakfast (not just cold cereal but eggs and bacon type) and some afternoons they have a complimentary cocktail.
Depending on the time of year, mulitple conventions can be taking place at the same time (the convention center has multiple concourses) and the surrounding business class hotels (especially I-Drive) can start to fill up quickly. For example, we waited too long to make our arrangements last year and for the quantity of rooms my company needed we had to move to the StayBridge's sister property in LBV. It wasn't horrible, but the I-Drive locale is much nicer.
