WebERP is prominently featured on this site.  Happy to announce that WebERP 3.09 has just been released.  New features with this version:

Multi-currency bank accounts, with revaluation of foreign currency balances
Automatic retrievable of European Central Bank exchange rates
Audit Trail logging of which users performed which functions at the transaction level
An API to allow external applications to retrieve webERP data - after authenticationAn xml-rpc interface to the API
Improved error handling in many scripts to highlight the field at issue. Code to limit the possibility for XSS attacks
Option to prevent the system from allowing inventory to go negative