Our API directory now includes 96 stocks APIs. The newest is the Eurex VALUES API. The most popular, in terms of directory page views, is the Bloomberg API. Below you'll find some more stats from the directory, including the entire list of stocks APIs.
In terms of the technical details, REST and XML lead the way. There are 55 stocks REST APIs and 42 stocks SOAP APIs. Our directory lists 64 stocks XML APIs and 18 stocks JSON APIs. 
The most common tags within stocks are 53 financial stocks APIs, 46 finance stocks APIs and 18 trading stocks APIs.
On the mashup side, we list 15 stocks mashups. We named Stock Price Scanner as mashup of the day in June. For reference, here is a list of all 96 stocks APIs.
360T API: Stock Trading Service.Track this API
ABN AMRO Markets API: Dutch stock market information service.Track this API
Related: Top 10 Financial APIs
Backstop API: Alternative asset management software.Track this API
getQuote API: Real-time stock price data.Track this API
Bclear API: Over-the-counter securities trading service.Track this API
Bloomberg API: Financial markets data service.Track this API
BSE Stock Quotes API: Indian stock exchange information service.Track this API
CDYNE Delayed Stock Quote API: Stock quote service.Track this API
Collective2 API: Stock trading system automator.Track this API
Deutsche-Boerse VALUES API: Financial Information Exchange Service.Track this API
E*TRADE API: Access to E*Trade services for applications.Track this API
Easy-forex API: Forex trading platform.Track this API
Empirasign API: Security markets data and trading model provider.Track this API
EODData API: Stock market historical data.Track this API
eSignal Market Data API: Stock market data service.Track this API
Eurex VALUES API: Financial Exchange Service.Track this API
EZX iServer API: FIX Routing and Normalization Service.Track this API
Financial Content JavaScript Quote API: Market data and stock quotes service.Track this API
Financial Content XML Quote API: Stock and market price data service.Track this API
FinancialContent Fundamental Data API: Stock and market price data service.Track this API
FinancialContent Stock Chart API: Stock market charts creation service.Track this API
FinancialContent Symbol Map API: Stock and market price data service.Track this API
Finotec API: Stock Trading Service.Track this API
ForexYard API: Automated Trading Service.Track this API
FreeStockCharts API: Stock and financial market data and charting service.Track this API
FuturePrice Data API: live NYSE shares feed.Track this API
Gama System Stock Quotes API: Stock and index value data service.Track this API
Google Finance Portfolio API: Investing portfolio services.Track this API
ICE Data API: Global securities market data service.Track this API
JunoTrade API: Online stock trading service.Track this API
Just2Trade API: Securities Trading Service.Track this API
kaChing API: Social investment service.Track this API
Knight Hotspot FX API: Market Data Service.Track this API
LMAX Exchange Trading API: Trading and Market Data Service.Track this API
MadScan Signals API: Financial Data Filter Service.Track this API
MarketConnect API: Italian securities market information service.Track this API
Marketiva Streamster API: Online trading service.Track this API
Markit Data API: Market Data Service.Track this API
MBT Quote API: Stock Quote Service.Track this API
Mergent Annual Reports API: Business information service.Track this API
Mergent Company Fundamentals API: Business information service.Track this API
Mergent Corporate Actions and Dividends API: Business information service.Track this API
Mergent Executives API: Business information service.Track this API
Mergent Historical Securities Data API: Historical stock service.Track this API
Millistream Market Data API: Securities markets information service.Track this API
Myfxbook API: Forex trading service.Track this API
NASDAQ Data-On-Demand API: NASDAQ historical stock quote data servcie.Track this API
Online Commodity Broker Certigo API: Futures/Commodity Trading and Quote Service.Track this API
OptionsXpress API: API and Mobile Trading Platform.Track this API
Orbis API: Electronic financial trading service.Track this API
PowerOptions API: Options Trading Service.Track this API
RestFul Web Services Financial API: Suite of financial services.Track this API
SEC Watch API: Corporate filings service.Track this API
ServiceObjects DOTS Fast Quote API: Stock quote and information service.Track this API
SixFinancial API: Financial Information Service.Track this API
StatPro API: Financial portfolio analysis service.Track this API
Stock Market Data API: Stock market data service.Track this API
Stocklytics Company Data API: Company Data Lookup Service.Track this API
Stocklytics Historical Stock Prices API: Historical Stock Price lookup service.Track this API
Stocklytics Stock News API: Stock news service.Track this API
Stocklytics Stock Tweets API: Realtime tweets about stocks.Track this API
StockTwits API: Real-time idea network for investors and traders.Track this API
StrikeIron Midnight Trader Financial News API: Financial news service.Track this API
TaqTiqa API: Historical Financial Market Trades and Quotes Service.Track this API
TD Ameritrade Veo API: Financial advisor platform.Track this API
TradeKing API: Stock trading and investment service.Track this API
Tradervue API: Stock trading journal.Track this API
TTAGG Stock API: Stock Data Service.Track this API
TurboTrader API: Open Trading Service.Track this API
WorldDataSource API: Financial Data Feed Service.Track this API
XigniteBondMaster API: Reference data for active and mature bonds.Track this API
XigniteBonds API: Bond price data service.Track this API
XigniteBondsRealTime API: Real time bonds price data service.Track this API
XigniteCorporateActions API: Corporate actions data service.Track this API
XigniteEarningsCalendar API: Earning calendar information service.Track this API
XigniteEnergy API: Energy futures quotes service.Track this API
XigniteExchanges API: Provides operating hours for world securities exchanges.Track this API
XigniteFundHoldings API: Mutual fund holdings disclosure service.Track this API
XigniteGlobalBondMaster API: Corporate bond information service.Track this API
XigniteGlobalFundamentals API: Stock fundamentals lookup service.Track this API
XigniteGlobalRealTime API: Real time international stock quotes.Track this API
XigniteHistorical API: Closing prices for U.S. equities.Track this API
XigniteIndices API: Closing index values for U.S. and world indices.Track this API
XigniteInsider API: Real-time corporate insider transactions.Track this API
XigniteLogos API: Company logo service.Track this API
XigniteNASDAQLastSale API: Stock price service for NASDAQ listings.Track this API
XigniteOutlook API: US financial market daily news updates.Track this API
XigniteQuotes API: Market quotes for U.S. equities and ETFs.Track this API
XigniteRealTimeOptions API: Options price quotes service.Track this API
XigniteReleases API: Company news releases.Track this API
XigniteScreener API: Equities screening service.Track this API
XigniteSecurity API: Global Securities Master Listing.Track this APITrack this API
XigniteSecurity API: Stock exchanges master company lists.Track this APITrack this API
XigniteTranscripts API: Earnings calls transcripts service.Track this API
XigniteVWAP API: Volume-Weighted average stock price tracking.Track this API
XigniteWatchLists API: Symbol based watchlist management.Track this API
Zacks Financial Data API: Investment research service.Track this API