Well, I haven't tried this.. but it should work:
HTML Code:
<if condition="$userinfo[fieldxx]">
<a href="$userinfo[fieldxx]" target="_blank">$userinfo[musername]'s Myspace</a>
</if>
Just change "fieldxx" to whatever field id your myspace profile field is.
The above code is pasted into the MEMBERINFO template. Where? Well, pretty much wherever you want it to show up.
You can also make the "$userinfo[musername]'s Myspace" part a phrase if you're picky like I am.