Google will only send an email once a day (or once a week) or as it happens. However, if you choose once a day or week, then Google will only look for your search term(s) once a day or week. It does not backlog alerts and send them in a bunch. Google will, however, alert you to Web pages as well as news.
Yahoo! has pre-set topics like Best Fares, Movie Recommendations, Stocks, Sports, Breaking News, News, etc. Google just asks for your search terms.
If you set Yahoo! up to send alerts to your cel phone, for instance, and your phone company charges per text message, you can set your alerts to a few as 5 per day or as many as unlimited.
There are also free reminder Web sites so you never need worry about forgetting a birthday or anniversary again! You can set it up to remind you up to 2 weeks in advance and to remind you every year!
For more information see: