Having browsed through drupal.org with no results for D7, let ma ask the public: does anyone know of a Search module that would extend the search by taxonomy terms? I have a very taxonomy-intensive site, where each taxonomy term has a rich description field, as well as its own term page. I want user to be able to find not only nodes but also taxonomy terms.
I'd highly recommend using Search API with which you can create an index and custom search from any entity including Taxonomy terms. You can then customize your search page using Views.
Try Custom Search Included submodules Custom Search Taxonomy: taxonomy options for the search block Custom Search Blocks: provides additional search blocks, with different settings Custom Search Internationalization
We faced a similar challenge where a large number of taxonomy terms contained valuable content that was not caught by the Drupal search index net. Our solution involved a small custom module. The module defines a custom content type with only a title field and term reference field. After a sitebuilder creates this custom node and chooses a taxonomy term to reference the standard node-centric index and search mechanism will find and display the custom node which contains only the title, term description as defined by referenced term, and a link to the taxonomy term page. By design this module requires a node to be created for each taxonomy term that the site builder wants represented. We created these nodes manually as not all taxonomy term descriptions were populated.
This basic module code is in 'sandbox' status.