I just keep a flat text file for all my accounts: checking, savings, credit card. For checking I just put the date, memo, transacation amount on each line, sort of mimicking the old check book ledger. Then I wrote a perl program (one of the benefits of having programming skills) that will add and subtract all the transactions to the penny.
Then with each months statement I balance the checkbook, crossing off everything thats in the statement. Works well.
I keep a log by year of stuff I buy, rounded up or down to the nearest dollar, it's just a running flat file as well. I use the same perl program to add up how much stuff I've spent.
If what I buy has a serial number, I put the serial number in the description field. Great for insurance purposes
System works pretty good, I can grep for "ammo" for example, and specify a wildcard for the filespec and find how much I've spent on ammo over the years.