Data Analysis:

• Anaconda+Spyder (MATLAB-like IDE for Python)

Vector Illustration Software:

Used for creating high quality diagrams for publications.

Free:

• Diagrams.net (my personal favorite)
• Inkscape

Non-Free:

• Affinity Designer
• Adobe Illustrator

3D Rendering:

• Blender

Circuit Simulation:

• LTSpice

Information:

• RP Photonics Encyclopedia (useful information regarding optics and photonics)
• Electromagnetic Waves and Antennas (Sophocles J. Orfanidis)

Send me a message if I should add something or if a link is dead.