I just extracted 2 small jQuery plugins from my blog which I use for displaying recent tweets from my Twitter profile and recent tracks from my Last.fm profile. Both plugins use the JSON APIs, and you can check them on my Github profile:

Clone the repositories, see index.html source for usage. And, read the source code if you are interested to build jQuery plugins.

Both plugins have dependency of 2 small jQuery plugins that you may also find interesting to use or just read their source code: