The reason I asked was to see if you should be studying harder or taking on more things.
If you are not in desperate need of money, and since you said you dont want to just kill time, then my advise would be take on something that helps your professional development.
A second language is an excellent start, especially English. You mentioned you were studying for a TOEFL?
I would refrain from writing a book on electronics. I am sure you are good, dont get me wrong. But I would buy a book if it offered that extra value from the unfiltered content online. To do this you need to have, some more than others, mastered the topic your book is concerned with, and this can take many years.
Since you like projects, you can setup or upgrade your lab at home?
Another thing you can do, is explore post-graduation opportunities. Maybe you can find an employer before graduating!
You can further develop your technical skills, like reading books on EMC, familiarising yourself with an industry-standard CAD package, get started on programmable logic devices (if you have not already) and so on.
Soft, transferrable skills are increasingly important too. Things that are seamingly simple, like presentation skills, report wrting skills, teamworking, project management etc will all arm you with the tools you will need for your future career.
Alex