I created this website showing tide times on a Google Map of the UK using tide prediction data from the Proudman Oceanographic Laboratory (POL) in Liverpool. The website has little commercial value but is allowed me to experiment with databases and the presentation of data, as well as SEO and marketing.
The server runs a script which downloads a different page from the POL website every fifteen minutes. Since there are 56 ports published online, the website has a complete up-to-date dataset in 14 hours, or by 2pm every day. The script extracts the tidal prediction data and saves it into a database ready for use by the main site. Special permission was kindly given by the POL for this, since their normal terms and conditions strictly forbids such activity.
Another script runs every minute, starting at midnight and continuing until 2am. It consults the list of ports and sends the day's tide times to that port's Twitter account, allowing Twitter users interested in such things - fishermen, surfers or even dog walkers - to have the day's tide times delivered automatically. This should only take 56 minutes to cover the 56 ports, but I've allowed an extra hour for 'retries' - times when Twitter may be down or experiencing severe load.