I started getting (more) serious about paying down debt last October. So, I was curious how much I had paid in interest on non-mortgage debt the year prior to getting serious compared to how much I've paid the year since. Here are my approximations. I think they're pretty close.

Nov. 2009 - Oct. 2010: $3,480 spent on interest.
Nov 2010 - Oct. 2011: $2,090 spent on interst. Of course, Oct. is a projection.

I then projected an estimate for the next year, based on current balances and payments. My total projection for the next year is: $1,240 spent on non-mortgage interest.

Each year, according to my estimates, I'll have spent about 60% of the previous year's total.

One thing my previous year's estimate does not include is late fees and bank over-draw charges. So my 2009-2010 estimate is probably even greater than $3,480.