I've been thinking about going this route for my readings. But I want to make it searchable so I can go back and find a reading easily, say search on a given card and see what readings it has come up in and how I interpreted it. My thought was to go with a database as I've had some experience with them quite a bit at work. If you have Microsoft Office, you could create such a database, then create an entry form which looks like a journal page. If you don't have Microsoft Office, I would recommend "Open Office" (available at "openoffice.org" ... it's a free, open source, office suite with word processor, database, spreadsheet & a couple of others).
A database like this would have the advantage of being readily searchable. I don't know what search capabilities the previously mentioned journal / note type programs might have. Then again, those programs would work very well if you weren't concerned about searching for particular items, or using it as a catalog of readings. But a database would be easy to sort different ways (obviously by date, but you could also sort by which deck is used for example, or by the name of the person you read for, or the spread you used).
Also, if you have little or no experience with databases, creating such a thing could be a little daunting. But, like I said, I have some experience with building these kinds of things, so it's kind of what I think of right off. Though the idea of entering all the readings I've done since about 1993 is a bit intimidating.
Hmm ... I wonder if others would be interested if I did create such a thing? I wonder if someone already has?