• Grails 1.0 has been released - with support for GORM, REST services and so on
• Speaking of GORM (Grails Object-Relational Mapping), you can find a good article on the technology here
• JRuby 1.1 RC2 has been released and as Charles says
  

  If you haven’t looked at JRuby, now’s the time to do so.

• Annotations
• Enums
• Static Imports
• Generics

but there are a lot more new features.

The official release note can be found here.
You can also find an excellent introductory article by Guillaume Laforge on InfoQ

Simple Groovy builder that uses StAX API to generate XML/JSON documents

Download

You can download the builder here

Source

Source code is currently available at http://code.google.com/p/dynawork/source.

Example

Here are a few examples taken from test cases

Creating XML using Woodstox

WstxOutputFactory factory = new WstxOutputFactory()
StringWriter writer = new StringWriter()
StaxBuilder builder = new StaxBuilder(
    factory.createXMLStreamWriter(writer)
)
builder.root1(a:5, b:7) {
    elem1('hello1')
    elem2('hello2')
    elem3(x:7)
}
assert writer,
"""<root1 a="5" b="7">
<elem1>hello1</elem1>
<elem2>hello2</elem2>
<elem3 x="7" />
</root1>"""

Creating JSON using Jettison

MappedNamespaceConvention con = new MappedNamespaceConvention();
StringWriter writer = new StringWriter()
MappedXMLStreamWriter mappedWriter
    = new MappedXMLStreamWriter(con, writer);
StaxBuilder builder = new StaxBuilder(mappedWriter)
builder.root1(a:5, b:7) {
    elem1('hello1')
    elem2('hello2')
    elem3(x:7)
}
assert writer,
"""{"root1":{"@a":"5","@b":"7",
"elem1":"hello1",
"elem2":"hello2",
"elem3":{"@x":"7"}
}}"""

Here’s the snippet from the announcement:

This project will be open for prototyping
JVM features aimed at efficiently supporting
languages other than Java.

The emphasis will be on completing the existing
bytecode and execution architecture with general
purpose extensions, as opposed to a new feature
for just one language, or adjoining an unrelated
new execution model.

The emphasis will also be on work which removes
“pain points” already observed by implementors
of successful or influential languages, as opposed
to more speculative work on unproven features or
niche languages.

It is definitely a step in the right direction for making Java a true multi-language development platform.