What sort of work do you do. ISO9000 formerly BS5258 simplay a third p[arty auditted quality system which looks at your procedures and practices and essentially checkes that you do what you say you do. It creates one almighty paper chain. That is fine for big companies such as that for which I work but for small comapnies it is an expensive luxury which IMO would be of little benefit. You can have a fully working quality system in place without the need for ISO accreditation. An example would be as follows.
I train people to install flowing anhydrite screeds. One of the thinbgs I encourage them to do is keep daily work sheets whereon they log details of the site they are working on, the quality and nature of site preparation, times of deliveries along with ticket numbers, the results of the on site testing they do prior to pumping the screed along with some other bits and peices. This day sheet forms part of their audit trail so that if there are questions later on in the process they can easily be referred to and the issues quickly resolved.
They don't generally need this information to be auditted by a third party although some of the bigger screed outfits have ISo 9000. For a bigger company it is very different. Many of then bigger main contractors would require a sub contractor to have this sort of accreditation as they will need to generate method statements, health and saftey compliance documents etc etc and make sure that their procedures are controlled.
It is much easier to controll your company's activities if you are a one man band with maybe 2 or 3 people working for you.
Hope this helps...
the link from girl racer red looks useful if you did want to go down the ISO route
good luck