Stefano Zacchiroli and I released ledger2beancount, a script to convert ledger files to beancount. Ledger is a bookkeeping system based on text files. Beancount is another tool which follows a similar approach but which from my point of view is the way forward.
ledger2beancount supports most of the features and syntax of ledger. It also includes some features to improve the conversion from ledger to beancount. The supported ledger features are described in the README and there's a manual with detailed descriptions of ledger2beancount's features. There's also an illustrated example showing some of the differences between ledger and beancount.
Martin Blais released beancount 2.0 a few days ago, so this is a good time to give it a go. Beancount has a web UI called fava which is absolutely fantastic.