I have successfully kept the following species indoors from mid-september to mid-may for the past ten years:
Ficus retusa, macrocarpa, nerifolia
Fukien Tea
Sageretia
Serrissa
Texas Ebony
Grewia
Calliandra
The two most important and limiting factors when growing tropicals indoors are light and humidity. As for the latter, a decent hygrometer is a must (shouldn't cost more than 40$). Now, obviously you can't keep your house at 60% humidity, but I've found that even my sageretia--which by all accounts are humidity loving trees--do not need heavy misting if the humidity in my house stays above 35%. That said, my Dad, who lives in western Canada, often sees indoor humidity levels in the teens. What I recommend in such conditions is to buy yourself a large used aquarium with a lid, and display your trees in there. So, get yourself a hygrometer, and see what your average indoor humidity is like.
As for lighting, I use a 1000 watt metal halide on a light mover over my large specimens, a 600 watt on a light mover over my figs, and 15 4' High Output T5's in my propagation room.
This, of course, is not a cheap set-up, and my electricity bills rival my mortgage payments, but you needn't start out with something this elaborate. For trees 14" and under, a bank of 4 - 5 T5 high output fluorescents will do just fine. Of course, if you just want your trees to survive winter, rather than thrive, then placing them in south/west facing windows will suffice. But why not start with one light, then next month add another, and so on.
Finally, you need to pay close attention to watering indoors. I find that despite the dryer indoor atmosphere, it still takes a lot longer for trees to dry out inside. This is where your soil mix comes into play. I use the following for all my tropicals: 30% orchid growers bark (you'll have to find someone who sells the small stuff 1/8 - 3/8"), 30% Turface (If you can't find turface, go to your local big box hardware store and ask whether they have "Shultz Aquatic Planting Soil"), 30% Crushed lava 1/4" size. Sieving is a must! This is a fast draining mix, and most of my trees need watering three times a week while indoors. More interestingly, this mix has an neat property: while excess water drains completely, the lava tends to hold small amounts in its highly porous surface. This means that when outside, even on the hottest days (100 degrees plus) in full sun, none but my smallest/shallowest trees need more than once a day watering.
I like to use a 25 gallon reservoir to store water. At the beginning of the week I fill it from the tap, then add fertilizer and aerate it with a small air stone or mixing pump (never leave water stand motionless for longer than a day; aerating stabilizes Ph and speeds up chlorine dissipation). This way, when my plants need watering, I simply dip my watering can in the reservoir and water away. That said, a basic idea of what's in your main's water is useful. Try taking a darkly colored ceramic plate a filling it with water. Let the water evaporate and examine whether or not the plate has a left-over film. This will indicate a higher than normal mineral concentration in your water. If this is the case, you'd be well advised to get a filter for your bonsai water. Also, it is a good idea to let water stand (not motionless, but aerated) for at least 24 hours prior to using it. This is about the time it takes for chlorine to dissipate. Chlorine in small doses probably won't hurt your plants, but even small doses can kill colonies of beneficial micorrhizal fungi that aid in your plant's nutrient uptake.
A visit to your local hydroponics store can be a real eye opener. These guys are in the business of indoor gardening, and can be a wealth of information...So long as you can get over the constant use of the word 'man' and the frequent allusions to the other indoor plant.
Hope this helps.
