i am one of those people who has to fight for every centimeter of flexibility, especially in my lower-body. people think i am very flexible, but it took me 4 years of karate before i could touch my toes.
i have an hour long list of stretches that i do (when i remember- im working on making it a habit) as a going-to-bed ritual(at least it will be within a few weeks).
when my muscles get tight, i feel choppy, uncoordinated, weak, and awkward.
my mom (she teaches chiropractic patients exercises and stretches to help them heal faster) showed me a fun thing about muscles: they only contract. if you squeeze your fingers, then release. bed your wrist at a 90 degree-palm going forward- and try to squeeze your fingers without straightening your wrist, you can't really do it. it's because the potential energy of your muscle is all used up. the same amount of fibers that have been stretched can do more than those fibers if they are all bunched up.

I do a simple warm-up routine before every class, and a longer version before a performance. However, the best oblique stretch ever I learned in a Mardi Love workshop:

Sit on the floor indian style or in lotus postition. Lean to the right side and place that arm on the floor near your body with your elbow at a 90degree angle, hand pointing away from you. (In line with your body) Then reach across your body with your left, shoulders parallel to the floor, then roll open. The finished position has your left arm going over your body (think ballet) shoulders and head facing forward, chest open. Keep your bottom on the floor, and you'll really feel it. Repeat on the other side.

I know the floor stretch you're talking about! Actually, that type of stretch (with the opposite arm going over the head, and then down across the body, followed by "rolling up" with the spine) is an exercise I used to teach to my Pilates clients. There's a Pilates exercise on the Reformer called 'The Mermaid' that is very similar. It's definitely a great stretch! The rolling up part feels so good on your back, too! All of my clients used to love it.

I love hip openers before dancing. I always fit a series of lunges into my classes and my own workouts. But I'm probably one of the more extremes for stretches:

wrist and hands
arms and shoulders
full body-side stretches
lunges
deeper leg stretches
gluts
abs and back
ribcage
hips
and integrate the whole body back together

I go through this entire sequence on my instructional dvd as well if you are interested (Bellydance Core Fitness).