DH and I don't train together, but we do push each other on our rides. He rides at a faster pace, I can usually hang with him as longs as I keep a good draft. Sometimes I'll call out to him to slow it down a bit.

Another thing we'll often do is split up. He'll head down one road and then come back on the next. While he's taking his little detour, I go "all out" and we see how long it takes for him to catch me. It's a cat and mouse game for us, and it's a lot of fun. Then we take it easy and recover for a bit and do it again. It's good interval training.