ActiveQuant

A java financial library and a trading application framework.

Advanced Stock Tracker

Web based application to keep track of stocks.

ASM

Santa Fe Institute "Artificial Stock Market" simulation model.

BeanCounter

Perl module. Stock market data analysis and performance evaluation. Both current and historical data can be retrieved and stored in an SQL database.

BlogTrader

Platform built on java. Pluggable architecture for custom indicators and charts.

Finance::Quote

Perl module to retrieve market data from Australia, USA, Canada, Europe, and a number of managed funds.

Finance::QuoteHist

Perl modules that fetch historical stock prices from the web.

EclipseTrader

Stock trading system including Level II/Market view depth. Written in Java run on Eclipse

GeniusTrader

Perl toolbox to create and back test trading systems.

iTrade

Charting and trading system written in Python.

ITSDoc.org

Investment and Trading System Documentation Project.

Lidgren

Charting with TA indicators. Written in Java

Marketier.org 

Online charting and analysis tool

Merchant of Venice

Stock market trading application with portfolio management, charting and genetic algorithm.

MAS

Market Analysis System (MAS). Analysis using technical analysis, charting, and automated batch processing of market data.

MATLAB Toolbox 

Open-source MATLAB tools for mechanical trading.

OJTS

Open Java Trading System.

QTStalker

Charting package using the portable QT Library.

QuantLib

Software framework for quantitative finance.

QuickFIX

C++ FIX (Financial Information eXchange) engine.

Robot Trader

Framework for back testing written in Java.

SMTM

Perl/Tk ticker, profit/loss calculator, and chart tool. Provides also: rquantlib, yahooquote and beancounter.

TADoc.org

Technical Analysis Documentation and Forum Project

TA-Lib

A technical analysis software library for software engineer.

Tradery.com

A free online trading community. Back test and optionally share strategies with others.

TsInvest

Computes the optimal gains of multiple equity investments.

XMLWorks

MarketAlert + Perl utility like "Reorder" price columns in ASCII files or generate point and figure in html.

XTrader

Charting software. Contains portfolio module. Linux and Windows.

Avidus

Charting, tech. analysis and trading strategy platform.

CapitalReSources

Manage and display market data (windows or web), use and define technical indicators, optimize trade systems

FFTS

Finicky Financial Trading System. Trading and risk management system.

FreeMarket

Was planned to be an analysis platform mainly build around a server architecture.

Gstockcalc

Calculates losses and earnings and can display a 30 day chart for each stock.

gChartMan

Charting software

GreatCharts

Draw charts: Candlestick, OHLC + functions like MAC, Stochastic, RSI, etc.

GStalker

Technical analysis charting package for GNOME

LibStocks

C library which can be used to fetch stocks quotes.

MFinance

Quantitative Finance Library aims to get people working on the lines of Quantlib, but implemented for Java, Matlab, S and R.

Nevada

An investment analysis and risk analysis system, especially geared towards hedge fund operators and fund-of-funds managers. 

Octopus

C++ Framework for evaluating position sizing, placement of stop-loss limits and usage of trailing profit stops. See also MaWaTT Trading Toolkit

ProfitPy

Python trading app. Works with Interactive Broker.

Risk Quantify

Support trading, risk management, accounting, and settling of FX, Interest Rate and Equity derivatives

ShareWatch

Written in Python, keep you up to date with share and derivative prices.

vtxboerse

Capture the rates of stocks from teletext in a MySQL database.

SlimFIX

Java implementation of the Financial Information Exchange (FIX) Protocol

AbleSys.com

Trading automation for day, swing and position trading of stocks, futures, commodities, forex & bond. Products: eASCTrend, WinTick

AnalyzerXL

Excel Add-Ins: TA functions, neural net, option&stock data downloader...

APT

Portfolio analytics and optimization

Ashkon Software

Data Downloader, Ticker Bar, back testing and charting apps

BNB-Software

Application for evaluation of business or portfolio performance.

Equis

Home of the popular Metastock development platform.

ESQuotes

Data downloader for Excel

QCollector

A data collection tool that works with Quote.com

LinuxTrade

Get access to real time quotes, charts , time and sales, fundamental and TA indicators, market movers, news articles, alerts, and Level 2 market depth indications.

MarketStream

M3 Market Data Server provides stock, index, future, option market data along with historical data and news databases.  

Modulus Financial Engineering

Tech. analysis lib for Windows/MAC/UNIX with C++, Java, Excel, VB, COM/ActiveX interface (and more). StockChartX, TA-SDK, Data Manager etc.

Nirvana Systems

Trading Applications: OmniTrader, VisualTrader and SignalWatch

PACT Consulting

SDK for myTrack to add live financial data to your applications.

Portfolio Insight

Help uncover hidden risks and opportunities in stock portfolios

SmartQuant

Offer data management, technical analysis, C++ scripting using CINT. Neural networking and portfolio management. Offer also the product QuantStudio.

Thinking Stuff

Automated trading platform. Build strategies by selecting and adapting rules with mouse clicks instead of using a script language. Supports Oanda.

TradingApp

C/C++ back-testing and execution framework.

TradeStation

A popular platform. Home of the "EasyLanguage" for developing trading systems.

TrendTrader

Direct Electronic Access trading. Real-time tick by tick, NASDAQ Level II, AMEX, NYSE. ARCA stop orders. Can handle conditional order.

Analysis and investment software that combines technical analysis with neural network and genetic algorithms.

Wealth-Lab

Develop and test your trading systems, and explore strategies contributed by other members.  They rank submitted trading systems monthly, so you see which strategies are working best.