I have looked at the SQL Server 2008 feature comparison matrix and it lists the express/web and workgroup editions as having the SSIS runtime. Does this mean it is possible
You need dtexec to run SSIS packages from command line.
In SQL2005 Express you got dtexec and necessary tools with
However, without SQL Agent you have to use other scheduling methods.
More information: http://daron.yondem.com/default.aspx?month=2006-05
Caveat: I haven't actually tried this and there are reports that dtexec just fails with a licence error. In my case, I just needed to run a dtsx once and did it with Developer edition with SQLExpress as data flow destination.