This paper discusses designs for integrating services in general and open programming services in particular into virtual machines. We draw on our experience with two systems. The first is Mozart, a programming system implementing the language Oz. Mozart's virtual machine provides a rich set of services for open programming, such as concurrency, persistence of data and code, components with dynamic linking, and distribution. The second system is Alice, which is at the same time a statically-typed variant of Oz, and an extension of Standard ML for open programming. Our design proposals for open programming services culminate in the definition of a virtual machine called SEAM, which we claim to be simple, efficient, and extensible. We substantiate these claims with preliminary performance results.