Quantum computing is rapidly evolving nowadays. We give below a nonexhaustive selection of tools that could be useful to anyone willing to start with quantum computation.
Drawing Quantum Circuits

basic quantum gates (from wiki).

quantikz from CTAN (Comprehensive TeX Archive Network), a simple LaTeX package to draw quantum circuits.

qcircuit from CTAN, another LaTeX package to draw quantum circuits (github).

QASM, the original circuit drawers used in the book of Nielsen and Chuang [with many examples].
Quantum Simulators and Frameworks

Qiskit toolkit (download, documentation, textbook). The Qiskit toolkit is a python package that can emulate a quantum computer or send in the IBM Cloud platform.

Quantum++ (github), a modern C++11 general purpose quantum computing library, composed solely of template header files. Quantum++ is written in standard C++11 and has very low external dependencies, using only the Eigen 3 linear algebra headeronly template library and, if available, the OpenMP multiprocessing library.

Google Cirq (website, github), the quantum language developed by Google.

Microsoft Quantum Dev. Kit (github, documentation and samples).

myQLM toolkit (download), a python package to perform quantum computing provided by Atos. Recently available on Mac using “pip install myqlm”.

softwareQ Designing Quantum Software (website), provides staq, a full stack software platform.
A more exhaustive list of quantum simulator can be found here.
An interesting website for a list of many quantum algorithms is the Quantum Algorithm Zoo.
Quantum Machine Learning Tools
 PennyLane (general website, qiskit version), a toolkit for Quantum Machine Learning.