This is due to be released in an upcoming module (along with the delegate mapper described here), however – here is a sneak preview of what I have been working on for Glass Mapper.
I think Glass Mapper is a fantastic and versatile ORM for Sitecore, however one of my slight bugbears with Glass Mapper as it stands is this. I want to build my POCOs as isolated as they can be. Glass Mapper has provided a fluent API which is grand, but the implementation by default leaves it a little short in my humble opinion. Out of the box, it’s a bunch of configurations that you add to the GlassScCustom (or in your own) class. In addition to this, if you want to support inheritance – say IExtendedSitecoreItem : ISitecoreItem you have to define all of the mapping for ISitecoreItem on IExtendedSitecoreItem as well. There are ways in Glass to sort this – using imports and the like, but you can end up with the framework excepting if you import the same thing twice. For me, I wanted an interface similar to that of fluent nHibernate, using a mapping generic to provide the mappings in an isolation from the original POCOs so I have created just such a thing: