Wetsuit accessories range from thermal pieces to wetsuit care and everything in between. If you are open water swimming in cold conditions then you may want to consider thermal neoprene swim caps, gloves or socks to keep your extremeties comfortable. Many of these pieces are for training use only and can't be used during actual races (check with your race director to know for sure).
Triathlete Sports offers several different lubricant options to aid in wetsuit entry/exit and to prevent chafing. These lubricants come in either stick or spray form and can greatly increase your comfort in your wetsuit while decreasing your frustration while putting it on.
Triathlete Sports also carries several wetsuit repair products to make simple neoprene repairs.