Instead of CharSet.forName, using com.google.common.base.Charsets from Google's Guava (http://code.google.com/p/guava-libraries/wiki/StringsExplained#Charsets) is is slightly nicer:
InputStream is = new ByteArrayInputStream( myString.getBytes(Charsets.UTF_8) );
Which CharSet you use depends entirely on what you're going to do with the InputStream, of course.