This is list collection of most popular CAD software list, we will keep this list up to date by adding and removing the software we find and come across.

2D CAD Software
SoftwareInformation
LibreCAD (OSS) LibreCAD is a open source 2D CAD software, and is a nice alternate to AutoCAD
QCAD (OSS) QCAD is another open source 2D CAD software
DraftSight (Free) DraftSight basic version if free
NanoCAD (Free) NanoCAD is complete 2D CAD Software
3D CAD Software
SoftwareInformation
FreeCAD (OSS) FreeCAD is a parametric 3D CAD Software and its our favorite.
OpenSCAD (OSS) OpenSCAD is script based 3D CAD software
BRL-CAD (OSS) BRL-CAD is another open source 3D CAD software
Autodesk Fusion 360 (Free) Fusion 360 is a cloud based 3D CAD, CAM, and CAE tool from Autodesk
Onshape (Free) Onshape is a full-cloud CAD system (web based)
PCB CAD Software
SoftwareInformation
KiCAD (OSS) KiCAD is a fully featured Open Source PCB CAD Suite, It has everything you need to create a PCB.
Eagle (Free) Eagle is a popular PCB CAD Suite, it is a good software but has steep learning curve(with some limitation)
Diptrace (Free) Easy to use full fleged PCB CAD Suite, with some limitation.
ProfiCAD (Free) ProfiCAD is designed for drawing of electrical and electronic diagrams, schematics, control circuit diagrams etc.
Qucs (OSS) A GUI based on Qt for setting up electronical circuits and a simulator
LogicCircuit (OSS) LogicCircuit – is free, open source educational software for designing and simulating digital logic circuits
FreePCB (OSS) FreePCB is a open-source PCB editor software that is easy to learn and easy to use, yet capable of professional-quality work.
Fritzing (OSS) Fritzing makes PCB desing very easy in a creative fun way for anyone, You desin a PCB within a hour
TinyCAD (OSS) TinyCAD is a program PCB layout programs, and can also produce SPICE simulation netlists. It is also often used to draw one-line diagrams, block diagrams, and presentation drawings.
gEDA PCB (OSS) PCB is another interactive printed circuit board desing suite like KiCAD and Eagle

Acronyms: OSS - Open Source Software, Free - Shareware/Freewares