I need to use a database in conjunction with iweb in order to effectively allow users to search by location, product type, new/used etc... is this possible?

I was wondering if I could create events or something in "iPhoto" and then attach what I think is called a metatag to each photo listing location, new/used, product type etc...

Other people must have had the same problems, can anyone please help?

What I would suggest you to use are sortable tables
http://iwebfaq.org/site/iWeb_Tables.html
where people can reorganize the entries by a certain criteria or use a WordPress blog which provides the ability to use categories and tags to categorize/sort the posts.
http://iwebfaq.org/site/iWeb_Blogging.html
WordPress also provides a search feature.

Regards,
Cédric