1. Google Custom Search Engine - Site search and more
Have a website or collection of sites you'd like to search over? With Custom Search Engine, you can harness the power of Google to create a search engine tailored to your needs.
http://www.google.com/coop/cse

2. Google Site Search
With Google Site Search, you can put a Google search box on your website and enable prospective visitors and customers to find information instantly.
http://www.google.com/sitesearch

3. PicoSearch.com
Enable your website visitors to search your own site.
http://www.picosearch.com

4. Site Search from Bravenet
Site search and free site search by bravenet.com. Let visitors search your site.
http://www.bravenet.com/webtools/search2

5. JRank
Are your visitors getting lost on your website? Put a search engine on your web site to help your visitors find the content they're looking for. Completely free, lightning fast, and super-easy to use.
http://www.jrank.org

6. FreeFind.com
Free search engine for your website. FreeFind.com lets your visitors search your website. Add a search engine to your website today, for free, in less than ten minutes. This is the fastest and easiest way to add professional level searching to a website.
http://www.freefind.com

7. Atomz Site Search
Atomz Site Search: The premier free search tool for your website.
http://www.atomz.com

8. CoffeeCup Flash Website Search - Add Customized Search to Your Website in a Flash!
Add a Search Engine to your Website Quickly & Easily
http://www.coffeecup.com/website-search

9. CyberSiteSearch
CyberSiteSearch site search tools, merchandising & search marketing features increase traffic and sales for online e-commerce websites of all sizes.
http://cybersitesearch.com

10. Site Search Specialists
Website search engine software for enabling customers to search your website effectively resulting in better website analysis like Automated Search Engine Optimization, Automated Pay Per Click Campaigns, Site Search Feedback Tool, etc
http://www.sli-systems.com/site-search.php

11. Clusty Site Search
Use Clusty to search your website! The forms below can be added to your site's HTML, to provide a web form from your page to cluster the web with Clusty. You can limit searches to a specific tab, the sources you like best, or even just results from your own website.
http://clusty.com/sitesearch

12. Omniture Site Search
Web Analytics and Online Business Optimization Platform by Omniture. Web Analytics, Online Business Optimization, Search Management, and More.
http://www.omniture.com/en/products/sitesearch_an~

13. WrenSoft Website Search Engine Software
Use the Zoom Search Engine to add a search function to your Intranet, CD or website. No ads & no annual fee. PDF support and more.
http://www.wrensoft.com

14. Site Search ASP.NET
Site Search ASP.NET is a .NET software component allowing search functionality to be easily integrated into your website.
http://www.sitesearchasp.net

15. Website search engine software: Create Search Engine for your online website, Intranet, CD and DVD in Minutes!
Website search engine software: Create Search Engine for your online website, Intranet, CD and DVD in Minutes!
http://www.mtopsoft.com/sitesearch