service lets you invoke Mac OS X's Services from the command-line. In a sense, it is the opposite of ThisService, which lets you use command-line tools as services.
You need to have MacRuby installed to use service.
Download the repository, cd into the directory and do rake then rake install. You might need to sudo to install, which will require you to be an administrator. You can do rake clean if you want.
If you want to get rid of service for some reason, just do rake uninstall.
service [-q|--quiet] <service-name> [<string>]
service applies service-name to string, or to the contents of STDIN if no string is given. The name of the service must be provided exactly as it appears in the Services menu, including capitalisation.
By default, service will output the result of the Service. For services that do not appear to produce output, this will usually be the same as their input. To suppress this output, use the -q option.
If you have a text document which you want to summarise automatically with the (somewht painful) SummaryService application:
< file.txt service Summarize