Reciprocal Link Checker - Enter the URL to search for. Second, input in the textbox the listing of the websites where you have done link trades. The spider will crawl one by one each of this addresses looking for links towards your website within your's link partners HTML code.

Redirects and your server result codes - This tool will check your server headers and the HTTP result codes it returns. It will follow any redirects it finds along the way, whenever possible. With this tool you can check to see how your server is redirecting and if your server is returning 404 for URLs which do not exist.

Reverse Keyword Lookup - This tool was designed to allow you to determine which keywords and phrases your competitors hold in Google.

Robots.txt Generator - Use this tool to generate a simple robots file for your website, allowing you to hide files or directories that you dont wish to be spidered. This generator tool is designed to create the text for the file for you and for you to then make changes should you feel necessary to afterwards.

Robots.txt creator - This tool will generate a robots file for your website and let you set the rules for robots of Google, Google Image Search, MSN Search, Yahoo, Ask/Teoma, GigaBlast, Scrub The Web, DMOZ Listing Checker and Nutch.

Robots.txt Syntax Checker - This robots.txt syntax checker checks the contents of a site's robots.txt against that contained in the latest specification, along with providing warnings on the use of new features that are not yet widely deployed.

ROI calculator (Yahoo!) - This calculator measures the ROI (return on investment) of a CPC (cost per click) advertising buy, such as Yahoo!'s search listings.

RSSxl - Convert an HTML Web Page to RSS - This online tool generates an RSS 2.0 Feed from pretty well any web page.