Gtk2Hs
- A GUI library for Haskell based on Gtk+. [Open source, LGPL]
- http://haskell.org/gtk2hs/

Java VM Bridge
- A bridge to the Java virtual machine via JNI for Haskell. [Open Source, LGPL]
- http://sourceforge.net/projects/jvm-bridge/

HaskellGnome
- Haskell Gnome and ORBit effort and bindings
- http://www.cse.unsw.edu.au/~chak/haskell/gnome/

Fudgets
- Graphical User Interface toolkit for Haskell and X Window system. [Free non-commercial use]
- http://www.md.chalmers.se/Cs/Research/Functional/Fudgets/

TclHaskell
- Useful for building graphical user interfaces through the Tcl/Tk. [Open Source, BSD-like]
- http://www.dcs.gla.ac.uk/~meurig/TclHaskell/

Gtk+Haskell
- Bindings for GTK+ for Haskell.
- http://www.cse.unsw.edu.au/~chak/haskell/gtk/

A Compiler Toolkit in Haskell
- A set of modules for creating compilers in Haskell. [Open Source, GPL]
- http://www.cse.unsw.edu.au/~chak/haskell/ctk/

MySQL-HS
- An interface to the database MySQL for the programming language Haskell. [Open Source, LGPL]
- http://www.volker-wysk.de/mysql-hs/

Haggis
- Multi-threaded, concurrent user interface framework for Haskell, X Window.
- http://www.dcs.gla.ac.uk/fp/software/haggis/

HGL Graphics Library
- A portable graphics library for both X11 and Win32. [Open Source, BSD-like]
- http://haskell.org/graphics/

FranTk
- A high level library for building GUIs in Haskell. It provides good support for developing complex dynamic systems, and is built on top of Tcl/Tk. [Open Source, BSD-like]
- http://haskell.cs.yale.edu/FranTk/

HOpenGL
- An OpenGL/GLUT binding for Haskell. [Open Source, LGPL]
- http://haskell.org/HOpenGL/

Regular expressions in Haskell
- Native Haskell implementation of polymorphic regular expressions. The regexps contains most of the features found in Perl.
- http://www.dcs.gla.ac.uk/~meurig/regexp/