Yes: Chakoteya, a fan-made but very reliable site.
From the site's front page:
This is your one-stop site for who said what and when on televised Star Trek and Doctor Who.
These pages have been created for educational and entertainment purposes only, and the content is decided entirely at my whim.
They are not here for you to copy onto your own website, so kindly respect that and just link in.
Chrissie, the site runner, has produced transcripts for all episodes of Star Trek (and also Doctor Who). It's a fan-made site - Chrissie is not affiliated with either ST or DW - but very well-made and very reliable.
For example, here is the transcript for the TNG episode First Contact, and here is an in-site search for the term "yacht". Here is the advanced search page, and here is a site map.
She also links from this site's front page to another site for Star Trek script searching. Currently this site isn't working (at least for me), but I thought it was worth mentioning in case this is just a temporary downtime.
As an aside, this site is very useful in finding quotes quickly to provide canon answers to questions on SciFi Stack Exchange ;-)