Since this place attracts freethinkers I'm expecting to get both practical and oddball advice, but what the hell - something might stick.

The situation:
Husband and I have been married ten years and we have a nearly five-year-old. We get on, rub along, tolerate each other well. There are no blazing rows, but times are tough and we are run ragged by various unfortunate life events (long-term unemployment = him, unsatisfactory employment = me; homesickness = me [I'm an expat]; the joys of parenting a very challenging and bright little boy [both of us]). We love each other, there is care and affection, but we are no longer in love. I find it nigh on impossible to manufacture any kind of spark between us - not sex (that's not the problem, per se), but passion. I find it amazingly easy to project desire, passion and even that magical in-love feeling on to others, but not my poor, long-suffering husband.

The question:
How in a long-term relationship does one fall back in love once that feeling has gone, gone, gone?

The postscripts/constraints
We're broke. We're knackered. We have maybe two hours each week night and three or four at the weekend. Babysitting is a very scarce commodity. We are very different people with different interests, aesthetics and social needs (we share a similar ethical outlook and have similar life goals).