Good Continuation
This navigation menu from all allmusic.com is a great example of Good Continuation because the elements are orriented such that they are in a perfectly straight horizontal line. I feel that the appearance of Good Continuation in this example is owed in part to the presence of other Gestalt Principles, such as Similarity, and Uniform Connectedness.
Proximity
UsabilityMatters.com's staff menu utilizes the Proximity principle effectively. While the buttons are of the same shape and size, they are organized such that members of certain teams are grouped together.
Similarity
ColorSchemer.com is just one of many sites that uses a Tag Cloud. Depending on their implementation, Tag Clouds notify the user of certain words relation to a search term or another constant. In this case, the the constant is the frequency of search (i.e. more popular words appear larger).
This is a good example of the Similarity principle because Clouds notify users of exactly how related elements are depending on their size.
Uniform Connectedness
Psdtuts.com provides a various ways in which visitors can subscribe to the page's updates and information. The above image nicely demonstrates how Uniform Connectedness can help the user to find related elements. This particular example uses uniform button size, spacing, and color