Online databases are a great way for Historical Societies to promote both their collections and their organisation.
Including records in a online database allows researchers to know about the range of items held by your organisation as well as specific items that may be useful for their research. In some cases the use of an online database may be the first time researchers become aware of the existence of your organisation. Researchers can then contact you for information on viewing or obtaining copies of items.
Participation in an online cataloguing project encourages standardisation of cataloguing in the use of fields required to adequately catalogue items. Using a thesaurus when selecting subjects makes it easier for researchers to locate items on a specific topic. One such online thesaurus is the Australian Pictorial Thesaurus.
Further discussion on this topic can be found here.