Which easy-to-handle software would you recommend me for creating energy level diagrams? What do you use and what is your experience? I'm recently working on my bachelor thesis and I would like to add some pictures to ilustrate Hund rules, Zeeman splitting, crystal field splitting and so on with option to customize them on my own. Cheers!
ChemDraw is a proprietary package that gives you easy access to renderings of orbitals, which can be useful here, but I do not recommend this.
I draw lots of simple figures in OpenOffice (free and portable) in the ODG format and save as PDF.
If you want to have orbitals to go along with your figures, then you should post a new question on orbital rendering programs because that is not within the scope of the question here.