For real-time streaming API a low cost option is IQFeed.net which charges about $67/month for Nasdaq, AMEX, and NYSE + $50 setup. The data feed source is ComStock and the only API available is through Windows COM (yeah, I know)

To offer real-time to the public you will need to set up agreements with each of the exchanges individually. Expect to pay about $1/user/month plus some fixed monthly fees.

If real-time isn't essential, you could also use the fantastic python library ystockquote to get delayed data from yahoo.

I used IB for few years. Recommend them highly. Not sure how much they charge these days. They're very flexible, have a great API and their transactional costs are cheap. You can get more info here: http://www.interactivebrokers.com/

i use IB as my broker too. I don't think they offer data sales separately.

Thanks. Did you use them as a broker or just for their data API?

Broker... but they have no minimums.

Can also use pipes http://pipes.yahoo.com/pipes/search?q=stock&x=7&y=7

most of the data pipes (not including graphs) didn't seem to be working...

that's my last resort, but I'd really prefer a real streaming API

Many years ago I looked into the problem, but for the Canadian market. We couldn't find a service with an API, so we took one of those 15$/month paying services that gives you some Java software to "analyze" the data (Stockwatch). I used a packet sniffer (Etherreal?) and reversed out the protocol. I used Python for the actual software. They don't really mind you doing that if you're paying already, so it was fairly easy to do, even for me who had no experience.

I must say sir. That is brilliant. $15/mth for a pseudo realtime quote API is dirt cheap.

If your application can tolerate a day's delay then perhaps you should look into just grabbing the XML files from Yahoo! Finance. They let you download the history of any of their stocks and use in your own code.

For example: http://finance.yahoo.com/q/hp?s=AAPL&a=08&b=7&c=..., and click on the download Spreadsheet link at the bottom

updown.com, an investing startup that really likes advertising to me on Facebook, uses these guys

http://www.quotemedia.com/

They seem to offer live quotes, but I cannot personally vouch for their services.

TD Ameritrade (http://www.tdameritrade.com/tradingtools/partnertools/api_de...) has an API, though I can't say I've used it myself.

Also, do you mind giving us a general idea of what you want to do? Hinting at a project without sketching out an outline is cruel.

That looks cool, but I'm with etrade an a little hesitant to change.

I use Cottonelle...After all, the market is in the toilet. (Forgive me, I see a need for humor here.)

With so many trading companies going bust I bet the price will go down soon.

you'll need to spend much more per month for raw streaming market data

Thanks.

try quotemedia, esignal etc.

Not techcrunch for sure!