Veiled Shadows

Here is a pretty awesome tool to connect to links hosting malicious code, spoof your Useragent settings, use a proxy, download malware, and deobfuscate and observer the source of hostile Javascript, pretty bad ass.  The tool is called Malzilla.  Then you can download the malware and analyze or reverse it. 

Malzilla

This can be used with other tools like Fiddler which is a web debugging proxy which can do all kinds of cool stuff.

Fiddler

Of course if you want to be sort of safe testing malicious links, run it through the Firefox plugin NoScript.