Easiest way to read Excel files in groovy?

One of my fellow GUG members has created a tool for working with Excel using Apache POI in very much the same way you describe. It's not formalized into a library yet (AFAIK) but is available on his blog.

It allows you to write code like this:

new ExcelBuilder("customers.xls").eachLine([labels:true]) {
  new Person(name:"$firstname $lastname",
    address:address, telephone:phone).save()
}

Check it out here: http://www.technipelago.se/content/technipelago/blog/44

POI is what your after http://poi.apache.org/ its a Java Lib so you can use it from Groovy. Not sure if there are Groovy wrappers for it anywhere