While I do toss some song or portion of song into each practice session, my primary goal these days is to become as competent as I can as an improvisor. I can play most things given the time to work it through (I do have speed limitations that I'm sure I could work on more, but I do work on speed as well in most practice sessions), but I have been spending the majority of my practice time working over jam tracks, just improving over various chord changes, working on both phrasing and originality when I can. I find the idea of jamming much more fun these days as learning others songs tends to get old to me fast. One of my favorite players lately has been Warren Haynes (Allaman Brothers, Gov't Mule, solo, ...) as I am really getting into that jam band mentality of going into something with no clear cut goal other than to create music, with someone laying down a progression and just going with it.
I realized several months back, probably almost a year ago now while taking lessons from a new teacher, that my improvisation skills sucked when each week he always wanted some free form improv and I found myself sounding repetative. Suffering from years of not playing with others, from sitting in my studio room working through others songs, it had just eroded from the minimal skills I had to damn near nothing unless I really thought it through. As I get better, perhaps I'll have the confidence to hit a few jam nights locally to put the pressure on, but I still have a ways to go before I'll be comfortable with that again (when I was young I used to jam with friends quite a bit, but between age and my long period of illness, it sort of fell by the wayside for many a year).
Long story short, just jam man - just get some backing tracks going and see what happens. I have more fun doing that than anything these days.