The Repository helper plugin can be used to install (local repository) or deploy (install plus deploying on a remote repository) multiple jars and their source zips in one pass. It is also possible to provide a pom.xml file, instead of using a generated one (with no additional dependencies). Just name the files as follows:
Create a directory (i.e. libraries), create sub-directories and put your files in them. The subdirectory path where the files are will be taken as groupId (slashes will be replaced with dots - leading and trailing dots will be truncated).
Here is a view of a file explorer:
SOME_DIR + libraries + org + springframework - spring-2.5.jar - spring-2.5-src.zip
Alternatively you can do it using a flat hierarchy:
SOME_DIR + libraries + org.springframework - spring-2.5.jar - spring-2.5-src.zip
In the repository these artifacts will be available with groupId=org.springframework, artifactId=spring and version=2.0. One will have no classifier (default) and the other artifact will have classifier=sources. FYI, the maven-eclipse-plugin tries to download artifacts with classifier=sources for each dependency of an Eclipse project.
For detailed usage see the plugin info page.