Whilst there are several ERP Software packages on the market SAP is the dominant player in the ERP market. Whilst initially only targetting major 30,000 people corporations, that market as they have implemented SAP in all such large companies in the main, they are now targetting smaller SME's requiring ERP software for businesses between 10,000 down to 500 people.
Be aware though SAP Implementations are not cheap, you will normally be looking at several millions to install the software possibly tens of millions. There are two ways of implementing an ERP system such as SAP
1.) Vanilla - This is where you pay for a basic install with no customisation, this is the fastest & cheapest approach.
2.) Customised - This is where you start paying huge amounts for an ERP system install, this is where you customise the software, the more you customise the install the longer it takes and the more you pay.
There are also longer term costs associated with an ERP install such as SAP. In say two years time they may bring out a new version of which for them to continue to provide you with ongoing support you may need to upgrade to a new version. This in it's onw right maynot be a large cost but if you have chosen option 2.) then you may end up paying for a full recustomisation (this is not covered under a standard upgrade) at a cost of millions or be faced with an ERP system the supplier such as SAP refuses to support unless you upgrade.
For the doubters out there I have bought two fixed price ERP installs, one custom and one vanilla, I have also seen someone buy in an ERP install on a time and materials basis, quote at an estimate of £5M and two years, the actual ERP install took four years and £17M.... I hope you have found this information useful ignore my experience at your peril.