ActiveResource isn't a particularly well written library, nor is it easy to extend, modify and use. It doesn't support certain features that I've come to consider essential for a Rails POX/REST client, like pagination. The only nice things you can say about it are that it works for the most common cases, and that it ships with Rails. But you know what hackers say about sucky tools - 'Don't get mad; roll your own'. So I did.
I started working on Wrest a few months ago with the intention of creating a drop-in replacement for ActiveResource. The section of the Wrest README that talks about Wrest::Resource is actually a record of the features that we've discussed over the dining table that we wished ActiveResource had. However, as I hacked away on Wrest, I slowly came to realise that a good REST client needs to be a good HTTP client first.
I took a look at those that were popular at the time, but they didn't really appeal to my engineering aesthetic. They heavily favoured class/static methods and seemed to be geared toward command line usage rather than as a library. So I started to implement a clean, easy to use and well encapsulated HTTP library first, resulting in Wrest::Core; it is now ready for use and is sufficiently mature that I'm comfortable writing about it and inviting people to take it for a spin. It does need a few more features, but nothing that can't be added with a few hours worth of hacking. Wrest::Resource however, is still a work in progress, but some of its building blocks are already ready for use. You can see some examples here.
Wrest is available for installation through both RubyGems and as a Rails plugin via Git.
To get the gem, all you need to do is
(sudo) gem install wrest. If you want it as a Rails plugin, simply do
script/plugin install git://github.com/kaiwren/wrest.git.
Wrest runs on Ruby 1.8, 1.9 as well as JRuby.
Here is an example that shows how you can use the Delicious API using Wrest. If you can't see it (it's a github gist that needs js) you can see the original source here. You may also be interested in the Twitter example, which showcases a more complex scenario with ideas and features from Wrest::Resource.