After thirty years of teaching math at U of Waterloo, I retired (in 1993) and became interested in financial math.
I found this stuff sometimes confusing, sometimes fascinating ... so started gummy-stuff.org.
(They say you don't larn something till you have to teach it.)

Because I seem to have quite a few readers, I get lots of e-mail.

I (usually) answer all of my e-mail, but I must warn you:

• I'm a lousy investor, so I can't (won't?) give investing advice.
• I write tutorials on subjects that interest me, so if you have an interesting topic let me know.
  (Indeed, many of my tutorials are motivated by e-mail.)
• At my age (74-going-on-90, as of 2008), I have a short attention span.
• Often, I start a tutorial then lose interest ... so it ends abruptly.
  (I usually intend to return to the topic, but often don't.)
• I wouldn't place too much confidence in the stuff on my website (or the spreadsheets)**.
  I do this for fun ... and don't use any of it myself !
  (Hopefully the tutorials will give you the "flavour" of the topic.)
• Although there's often a bunch of math stuff, there are also lots of pretty pictures and spreadsheets so you can just skip the math.

There may be links to .ZIPd spreadsheets in a folder called SS (which stands for - surprise! - spreadsheets), but the latest are always in the Excel folder.
I often massage spreadsheets (uh ... that means "correct bugs"). The corrected improved SS is always in the Excel folder ... un ZIP'd.

Then, too, I should point out that I often get e-mail which sometimes requires my spending hours to generate an appropriate reply.
(This might involve generating some formula or some charts or even a spreadsheet.)
I (usually) find this fun.

However, I often get no response to my reply ... and that ain't nice.
Just a simple "thank you" will make me so happy!!