First of all, the most important search engine to cater to is Google. More than 80% of all searches are through Google so if they know where you are and rank you high then that is all you need to have a successful website. You will need a Google Analytics account along with Google Webmaster Tools. This is free and easy to use.
One thing Google Analytics requires in order to link to your site is a sitemap in xml format. This type of sitemap is for no other reason than to appease Google. I used to create these manually by typing in the URL of each page into the xml file then saving it. Recently I found a "free" tool that does this automatically. Just go to http://www.xml-sitemaps.com/. Type in the URL of your site and it will crawl your site, analyze it, and create the text needed for your sitemap. All you have to do is copy and paste!
Another interesting and helpful tool is Hubspot's Marketing Grader. Type in your URL and it will analyze your entire site, letting you know what is correct, what works, what is lacking, suggestions on improving, etc. It will also give you a grade from 0 to 100. Sometimes it gets things wrong (It thinks this site has no link to the blog which it does!) but overall it is a valuable tool. It can be accessed at http://marketing.grader.com/
In the future I will throw more of these freebies at you.