This module creates a free tagging field from any CCK field that can contain a comma separated string value.
1) Create a view* or some other means of searching via a path argument.
2) Configure freetagger. Give it a path with a replacement token %, which will be used to search.
3) Create a CCK type and a text field. Check freetagging for the text field and be sure to select "Filtered Text" so that freetagger can output links.
When users make a comma separated list in the target field, it will be turned into a set of links to searches.
* This module recommends using views to create the target path, with a "Taxonomy: Term Name" argument for the term argument.
This module requires both CCK and taxonomy modules.