You are going to get so many different answers your head will spin. What kind of budget are you on? That will help to narrow things down a bit.
Sport photography typically requires fast glass (i.e. low 'f' numbers) and fast auto-focus but that is going to cost you some coin. For rowing you can probably get by on a consumer-grade lens. Again, it depends on your budget. Reach would be just as important as speed. Take a look at one of the long zooms like the Nikon 70-300VR. Sigma also makes a few in the 300mm to 400mm range that are well thought of. I'm sure you'll get a dozen different lens suggestions from others (head-spin time).
Here are two good sites for lens reviews and info:
1)
Digital Photography Review
2)
Thom Hogan
"Other equipment" is a deep question. In my opinion there are three "essentials": 1) a bag (you already have one, but only one?), 2) a sturdy tripod, and 3) cleaning gear. Beyond that there are several hundred other "essentials" that you never knew you wanted until you read about them in the various catalogs and magazines. It's a deep hole.
Other bags are something you will discover the need for on your own. I have a bag for different needs (i.e. around-town, travel, hiking, etc). My wife says I have more bags than she has purses. I think she only says that because she wants more purses.
A good sturdy tripod is an absolute essential but be prepared for sticker shock. Good tripods are NOT found at Best Buy or Walmart. My tripod and ball head cost more than my camera body but they were worth every penny ten times over.
Which tripod to buy depends on several factors:
1) What is the total weight of your camera and
heaviest lens you plan to support? Will the tripod EASILY support them? You don't want to start off pushing its capacity limits.
2) What is the maximum height you need (i.e. how tall are you at eye-level)? 'Nuff said.
3) How do you plan to use it? For example, will you be carrying it a lot (i.e. hiking or traveling) or is it primarily intended for a fixed location (such as a studio)? For studio work you can use just about anything as long as it's stable. If you plan to carry it around town you may be better off with carbon fiber legs. They are usually lighter and easier to carry. Also, if it is to be stored in a suitcase then you probably want it to collapse down to 22" or less.
IMHO a good tripod is the number one most important accessory you can buy. Getting it right the first time can save you a bundle in the long-run. Wrong choices just sit in the closet. Do some research and ask a lot of questions. Again, budget is a huge factor.
Cleaning supplies is an entire topic in itself. One product I highly recommend is a
Giotto Rocket. I have several sizes and always carry one with me. Great tool.
Sorry so long winded. I'll get out of the way and let others chime in.