I used the repository pattern in implementing the guest book, so the videos are a good source.
The ContentMeta.cs, ContentMetaLink.cs and ContentMetaRepository.cs all are part of a good example and it is used on Admin/PageSettings.aspx.cs, the repository is declared at the top, and use of it can be found in the code section #region Meta Data
SavedQuery.cs and SavedQueryRepository.cs are another example used in /DevAdmin/Controls/QueryTool.ascx.cs
The Html feature has also been partially converted to the repository pattern but isn't a clean example like the above examples.
Hope it helps,