To the Top Martijn van Welie The users need to go back to the top of the page
From www.macromedia.com/
Pages are longer than 2 views and users are likely to go back and forth the top of the page. Typical use of this pattern is in combination with long page types such as an Article Page or a where the users jump from question to answer and back. Another situation is when displaying long texts and users need to get access to the navigation again. Provide a link to the top of the page at locations in the main content Choose strategic locations to place a link in the content labeled 'back to top' or just 'top' with or without and up-pointing icon. Strategic locations are typically paragraph endings or other types of 'blocks'. The link itself points to an anchor placed at the top of the page.
Basically this solution can be used for to reasons:

1. To get back to the main navigation
2. To get back to the top part of the content

If you are doing it for the first option, consider using a at the bottom of the page instead. Even having both a "to the top" link and a repeated menu can be a bit redundant but nevertheless useful for users. This allows users to go back the main navigation from almost every scrolling position. It may also be convenient for disabled users who scrolling is difficult to do. This example from Sony is taken from a product page that is several views long.

This example is from www.cooper.com where a Repeated Menu is combined with a "to the top" link in an Article Page.
Sony, Macromedia