Integrated Development Environments / RAD tools / GUI-builders on Linux:
General/Editors:
Amy (HTML, C, C++, Java, SQL, LaTeX, Makefiles and many more languages)
blIDE (incomplete; no downloads as of yet)
IBM's Eclipse (an extensible IDE kit; Java, C/C++, plus other languages via plug-ins that are becoming increasingly available, such as Perl via the EPIC plug-in)
Code Crusader (supports just about everything) with the Code Medic debugger
Glimmer
InfoDock
SGI's Jessie (doesn't seem to exist any more)
Emediat Solutions's RadBuilder
RHIDE
CYGNUS's Source Navigator with the Insight debugger
SciTE
Titano
WideStudio
wxStudio
Ada:
GNAT Programming System (GPS)
TIA (for GNAT Ada 95)
BASIC:
TrueBASIC (Linux version to be released soon)
C/C++:
Amy
Anjuta
ICS's BX Pro (for Motif/C++)
Code Forge's C-Forge
Code Blue
Metrowerks's Code Warrior
Bloodshed Software's Dev-C++ (for C/C++)
DiaSCE
IBM's Eclipse (an extensible IDE kit; Java, C/C++ in late beta, other plug-ins pending)
gIDE
Glade
GNAT Programming System (GPS)
CYGNUS's GNUPro
FLTK & Fluid (for C++)
IDEntify
KDbg
KDevelop
KDE Studio
Suite 3220 Software's Moonshine and Moonshine Professional
OpenAmulet
RHIDE
QtEZ (for C++ w/Qt)
Scintilla (for GTK+/C++)
Wind River Systems / TakeFive Software's SNiFF+ and SNiFF Penguin
CYGNUS's Source Navigator
with the Insight debugger
TogetherSoft's Together
VisKProg
MicroEdge's Visual SlickEdit
Q Software Solutions's Wedit
VDKBuilder
VIDE (for C++ and Java)
WideStudio
wxBuilder
wxDesigner
wxStudio (for C++ and Python)
Xwpe-alpha
Objective-C:
GNUStep's ProjectCenter
ECMAScript (formerly "Javascript"):
TrollTech AS's Qt Scripter (for the Qt Script extension of ECMAScript)
Nombas, Inc.'s ScriptEase (for ECMAScript)
Eiffel:
Interactive Software Engineering's EiffelBench
HTML:
Java:
Amy
AnyJ (for Java)
VioSoft Arriba
BlueJ
Chicory
Omnicore Softwar