Start by defining your needs and ressources. Then people will be able to help you. What do you mean by algo trading. A daily MA crossover or some tick by tick shit? You can't know where to start if you dont know where you'r going.
Alright, familiarze yourself with quickFIX (http://www.quickfixengine.org/) and pick up a few books on quantitative finance and computational finance. Paul Wilmott, Daniel Duffy, and Nassim Taleb have some books on Amazon.com that would be a good start for you.
You should pick a niche inside the market that would fit for you.
1. Gateways/order routing, see quickfix.
2. Algorithms/Event Processing, check out (http://esper.codehaus.org/about/nesper/nesper.html)
3. Pricing (See the books by the above authors).
4. Risk (check out some books by Carol Alexander).
PS: Ninja sucks in my opinion. Trading Technologies is much more friendly to our developers.