OpenERP (formerly know as TinyERP) is an open source ERP (Enterprise Resource Planning) software package. A lot of documentation and links still refer to TinyERP
OpenERP has a server and client install for Windows. Mac and Linux variations. The main Linux distributions have OpenERP in their repositories ready for an easy install. The latest version of Ubuntu (8.04) has version 4.2 still called TinyERP. For Windows there is client, server and all-in-one installers. Mac install is from source so may be a little more complicated see here.
OpenERP is a modular system and has modules for
Accounting and Financials
CRM
Human Resources
Inventory (Stock)
Manufacturing
Purchase and procurement
Sales and Marketing
As well as the standard client there is a web application which looks like this

As with many open source ERP software (OpenBravo and Compiere) OpenERP uses a PostgresQL database
Summary
Current Version
4.2.3
eTiny 1.0.1.1
Platform
Installation – Windows, Linux, FreeBSD, OpenSolaris
Database PostgreSQL
License
GPL
Well known Users/Case Studies
see http://openerp.com/success-stories.html
Useful links
OpenERP Site
OpenERP Wiki
TinyERP Virtual Appliance Server
Christophe Simonis – OpenERP Developers Blog
Relevant Blog – BeezNest Open Source Specialists

{ 4 comments… read them below or add one }
You make a mistake concerning the licence: OpenERP is not LGPL but GPL.
And the sourceforge project is not related to OpenERP; this is another (dead?) project written in java.
Christophe
Many thanks for correcting me and apologies for the error. I will correct the post accordingly
Another useful link is the launchpad project: https://launchpad.net/openerp
Christophe
I have also added your blog http://christophe-simonis-at-tiny.blogspot.com/ as a useful link. Hope this is OK. Thanks again.