Don't you hear it coming? Hiss hiss Choo choo! It's Ruby on Rails, making its way between so many web frameworks.
Struts is great in J2EE land, so it is Zope in Python world. However, if you love Ruby as much as I do, you have to give Rails a chance. And if you don't know Ruby yet... there's room for many a more! Get on board! :)
Ok, that's 'nuff, no more spam :) There's a drawback that I find particularly undesirable, if you plan to run RoR with mod_ruby you'll need to lower $SAFE to 0.
$SAFE levels are one of the greatest advantages of Ruby, you set it up (there are several levels with its definition, take a peek at Pikachu^WPickaxe Book) and the interpreter will stop you from doing insecure things. Essentially it is a way to dissallow the execution of untrusted code. It works this way: every object in Ruby has a "tainted" attribute, if you set it and you have $SAFE >= 1, that object will raise an exception, you'll need to "untaint" it to have access. It's very handy if you are doing web stuff, everything that comes from the user is tainted, so you'll need to check anything coming from the outside and then, untaint it. If you raise $SAFE your code will be even more restricted.
Nevertheless, I believe RoR will be the killer thingy that will give visibility to Ruby, everyone will hear about it soon. My impression is that it's already gaining momentum, sweeeeet :)
BTW, I'm now taking a look at Ruby Web Dialogs: use your web browser as a GUI, combine Ror and RWD and you'll get something really nice and innovative.