There is a version of ArcSDE that is licensed with ArcGIS Desktop 10 - at the ArcInfo license level. It works with Microsoft SQL Server Express.
This gives you the versioning and replication functionality of an ArcGIS Server based installation. It is important to remember that the data stored here will only be accessed through the ArcGIS license on your workstation. In fact, I think the databases created through this, have to be located on your local drive.
I have used this type of installation and it was very successful. If you have a number of users working remotely on the same dataset, and need to control data editing and synchronization between them, this works very well if set up on each remote workstation.