
If you're looking for a pose that will strengthen your shoulders and core, and increase flexibility in your spine then give Extended Tabletop a try. I like to move into this pose from a variation of
Three-Legged Dog with your knee bent (see the photo after the break). This is a pose I've only seen in Vinyasa Yoga classes, so it's a newer pose that will help prepare you for doing
Wheel.
Backbends are some of my favorite yoga poses. Since our bodies rarely have the opportunity to bend this way, not only is arching the spine a treat but it stretches the front part of your body quite nicely. Not only that, but increasing flexibility in your spine is a great way to stay healthy and avoid lower back pain.

Sitting with a rounded spine typing all day and biking hunched over takes a toll on my spine. All that rounding forward can make my back ache. I find that arching backwards, in the opposite direction of all the hunching, feels great.

Since I run a lot, my hip flexors and lower back get really tight, so I love stretches that focus on opening these areas, such as Scorpion. This is actually a yoga pose that's a balancing backbend. It feels amazing on the front of your body and your spine, but it's a really difficult pose to get into, let alone hold long enough to get a good stretch.

When you do
Bow pose on your own while lying on your belly, it's really difficult to get a good stretch in your spine because gravity is working against you. Flipping the pose over with help from a partner and trying it upside down feels amazing. The person on top will get an unbelievable stretch in her torso, chest, and shoulders, and the person on the bottom will greatly appreciate the pressure and support on his lower back.