I came across another alternative for custom reporting with mysql or postgres databases. You can use Open Office, Base module. You can use either ODBC, or the native Mysql, and Postgress database connectors. The native drivers are not installed by default, so you have to download and install them. The Mysql driver is an add-on from Sun, and the postgres one is from the drivers tab in the project section. Once you connect to the database, you can create queries and reports in base, or use the Sun Report Builder add-on for more drag and drop reporting. It looks like they will also be extending the report writing capabilities quite a bit in future versions, according to the project specifications. I tested with some simple reports using 2 tables with 1 relationship, and it seemed to work. I expect this alternative to become more sophisticated over time. Also, apparently the base program will be integrated with Pentaho business intelligence tools in the future, according to this article.
There is also an open source equivalent of Microsoft access called Kexi. I am just in the process of having a look. This one is the database component of the Koffice suite, but can be used independantly.