Firefly is a PHP based money manager. It's built to support my own finances, but can be used by pretty much anybody.
Firefly is pretty simple. First and foremost, Firefly can be used to create a bunch of accounts. Each account has an opening balance and a date for that balance. For example: your balance was EUR 100,- at the start of this year.
Once you have your accounts fixed you can start adding transactions. A transaction is either money coming in or coming out. It has a description and a date as well.
If you do this for a long enough time, you have a pretty useful financial overview. Firefly can generate charts and reports which you can use to keep an eye on your finances.
Please read more about this on the wiki pages.