Acow is a command line accounting application that I wrote as an experiment in the use of SQL (using MySQL in particular).
It is a relatively simple system, but supports multiple accounts and transactions between accounts. Note that the application is entirely console based, however, it could be combined with a graphical frontend.
The first version of acow was written in perl using the DBI database module to connect to MySQL. I also wrote a C version which uses text files in place of a database to store the account details.
Acow is available at https://github.com/sconemad/acow