"Do not follow your passion but always take it with you." [Mike Rowe]
Here I present unstructured Excel © topics which I found interesting:
What you should NOT do with Excel ©.
What is good programming practice when using Excel © VBA?
Are you an Excel © expert? This also suggests how to proceed while learning Excel.
Excel © Forums - You can learn something but do not expect too much.
Sometimes you do want to use Excel © VBA macros. On other occasions worksheet functions are just as fine.
Dealing with strings in Excel ©.
Get interesting infos about cell contents with Excel4 macro function GET.CELL or use a macro similar to that.
Some date functions and date formulas I found helpful.