I've started doing some running intervals/speedwork and notice that my hamstrings get pretty sore afterwards. I do some off-day stretching, although I probably could do more. Should I push ahead and deal with soreness, focus more on stretching or should I so some hamstring strengthening exercises? What would be a good regimen?
So they're just sore? Intervals hurt - that's the point - you want to be a bit sore because that's your body getting stronger.
Stretching's probably not going to help much. The intervals are doing a small amount of damage to your body so that it can then repair itself and a bit more and become stronger.
You need to rest and eat sufficient protein to help the process along.
This advice does not apply if you get a sharp pain - which might be a hamstring tear.
I have the same issue. My PT prescribed "eccentric leg curls." Put 50 or 60 lb on the leg curl machine. Pull slowly with both legs, then slowly return to the rest position with only one leg on the pad. Somehow this really helps the hammies. Just do three sets of ten. Increase weight with caution as you improve. Beware of too much weight or too many reps or pulling too fast; any of these can cause re-injury.
Couple things to do that might help:
Ensure you are hydrated. Proper hydration will reduce muscle soreness.
Take some type of recovery drink after the workout. I've used Endurox quite a bit. It speeds up recovery and assists with sore muscles quite well. There are other drinks/items out there as well that might work just as well, but Endurox is my drink of choice. If you cannot have something like this ensure to eat something fast after working out. The first 30 minutes after a workout your body needs fuel to recover quickly.
A weight training routine to augment the running might help as well. Muscle tend to atrophy if you do a lot of endurance running. Simple high-rep, low-weight exercises (leg curls, extensions, etc. might help bolster your legs a touch.
Lastly, ensure you strecth as Sarge mentions above. It's likely the soreness you feel is routine, but you need to ensure you don't tred too closely to injury.