Wine is an implementation of the Windows API on top of X and Unix. It does not require Microsoft Windows, but can use native Windows DLLs if they are available. It provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes.
GnuCash allows you to track bank accounts, stocks, income, and expenses. As quick and intuitive to use as a checkbook register, it is based on professional accounting principles to ensure balanced books and accurate reports. It is backed by an active development community and is blossoming into a full-fledged accounting system.
Citadel is an advanced messaging and collaboration system for groupware and BBS applications. Users can connect to Citadel using any telnet, WWW, or client software. Among the features supported are public and private message bases (rooms), electronic mail, real-time chat, paging, shared calendaring, address books, mailing lists, and more. Unlike other collaboration servers, Citadel provides its own data stores and is therefore extremely easy to install; you don't have to "bring your own" email and database because they're built in. The server is multithreaded and scalable. In addition, SMTP, IMAP, and POP3 servers are built-in for easy connection to Internet mail. Citadel is both robust and mature; it has been in production since 1987.
CUPS-PDF is a PDF writer backend for CUPS. It is designed to produce PDF files in a heterogeneous network by providing a PDF printer on the central fileserver. It will convert files printed to its queue in CUPS to PDF and put them in a per-user-based directory structure. It can execute post-processing scripts, e.g. to allow mailing the results to the user.
Kolab is a groupware system that provides a comprehensive and flexible solution for workgroups. Email, contacts, and group calendars can be managed via the Web, Windows/Outlook, and Linux/KDE. It supports offline synchronization and full seamless support of mixed client environments because the Kolab-XML storage format is fully open and avoids MAPI/TNEF.
RAPID provides stock/commodity charts, buy/sell tax accounting and trade profit graphing, plus dozens of technical analysis tools, including trendlines, point and figure, candlesticks, simple exponential and weighted moving averages, volatility, macd, stochastics, wilder DMI, standard deviation bands, trendlines, time-horizon lines, fibonacci, slope, momentum, OBV, CCI, bollinger bands, probability osc, cycle finder, derivative and integration chart, Williams Accumulation and distribution, etc.