Digg
http://digg.com/add-digg
You can easily display the latest Digg news on your site by adding a Digg Widget, now with more choices for what to show and how it's displayed. When news is updated on Digg, it will automatically be displayed on your site, in the format that you choose. Very customizable and no registration is needed.

HTML Validator
http://www.htmlvalidator.com/htmlval/urlform.html
Want to promote good HTML? You can easily place a form on your web page that lets your visitors enter a URL and then get validation results. The results are generated by CSE HTML Validator Lite. No registration is required and you can see the sample at work. Two different layout options are provided.

FreewareFiles
http://www.freewarefiles.com/content.php
Top ten freeware list added to your site with javascript code. If you have an RSS reader other feeds are also offered. No registration and links open in a new window.

RSS to Javascript Converter
http://www.theyardmart.com/rss_to_javascript_converter.htm
TheYardMart.com offers a nice RSS to javascript converter. If you know of a feed that you want to add to your site that is available in RSS, you can convert it to javascript by using the wizard provided. If you are not familiar with RSS or don't have a RSS reader on your site, this is a very useful tool. Please register of login to access this utility.

123Greetings
http://associates.123greetings.com/
This site makes it easy to add greeting cards to your site. Membership is free and you can customize the greeting card site with your logo and colors. Everything is hosted on their server and an affiliate program is available.

Website Submit
http://websitesubmit.hypermart.net/addscript.htm
This site offers a website submission service. Users can select the search engines they would like to submit their site to. According to what is shown, the service is free. If anyone has any experience with it I would appreciate any feedback you could provide.