For the last few years, I've been using a large Excel workbook to keep track of my personal finances. This worked well when I was living at home and my only expenses were Netflix and new hardware from Newegg. However, now that I'm living in an apartment, paying all my own bills I've found that keeping track of every transaction on a daily basis just doesn't scale to real life situations.
I've been playing around with Wesabe as a means of aggregating data from my various accounts for a few months now and haven't been all that impressed with it. Wesabe certainly handles data importing fairly well and their tagging interface is quite usable, but it just lacks a lot of the features I've become accustomed to in my Excel workbook (eg. custom graphs and future projections).
Now, I could use Wesabe's xls export feature and integrate it with everything else I've already got, but that would take quite a bit of work to keep thing sync'd and I fear that I would run into the same problems I currently have with scaling to large numbers of transactions. The alternative that I've chosen to pursue involves Wesabe's REST API mixed with some Django/matplotlib magic to generate all kinds of neat stuff on the fly from live data.
In the process of building this micro-economic paradise, I found that Wesabe's Python API is far from complete and was never intended to be more than a quick hack (nothing wrong with that, but sometimes you want more). I've written a more Pythonic, reusable Wesabe module. It's still a bit hackish and doesn't implement the entire Wesabe API yet (TODO: Financial institution, merchant, tags) but it's better than nothing. wesabe.py (pydoc)
This idea of a personal finance app is still a bit half baked, but I think it has potential. Hopefully I'll have something useful working soon.
I'm sure a number of people are going to tell me that this software already exists with Quicken or MS Money or MoneyDance but none of them do things the way I like to. I've never taken a real micro-economics class so I have a bit of a slanted way of looking at money, but it works really well for me and keeps me from spending too much money. I really like knowing exactly how much money I'll have six months from now (and being able to graph it).