Shimano Altus20

Terminology has changed a bit over the years. Used to be that a ten-speed had two chainrings and five sprockets at the rear. These days people tend to use something wich describes the configuration instead (as in 3x7).
But rear and front shifting are quite independent of each other, and most attention is usually given to the rear setup.

Basically you need a right brifter(brake + shift lever) that's shimano(or Shimano-compatible, I believe SRAM make some) in 7-speed. And also a left brifter for a triple crank.
Doesn't have to be Altus, can be (almost) whatever you stumble upon.
Anything in the Shimano range that isn't "flat bar, road" should do.

You will need to match brakes to levers though. Stuff in this category can have two different cable pulls, either for v-brake, or for canti brakes. There are ways to get around any mismatch, but better to get the right parts from the beginning.
You will most likely be looking at v-brake stuff, but bike parts die hard, and there is quite a lot of canti brifters still out there.

Otherwise, first course of action WRT shifters not working (unless obviously physically broken) is usually to hit them with something to loosen up gunky lube inside. Some shoot a can of WD-40 inside, some use brake/clutch degreaser. I've even read about people removing shifters from bars and dunking them in kerosene or diesel fuel. If they aren't working now, there's not much damage dome by trying. And at Altus you're not looking at much of an investment loss either way.

If you shop around, you should be able to find a pair of 7-speed shifters on eBay for $20.00 or less. This is what you need: SHIMANO ALTUS 7-SPEED SHIFTERS/BRAKE LEVERS ST-EF50 NEW - eBay (item 290472584085 end time Sep-13-10 10:14:04 PDT). Or try this: SHIMANO 21 SPEED ALTUS MOUNTAIN BIKE MTB SHIFTERS&BRAKE - eBay (item 290473098036 end time Oct-07-10 15:54:55 PDT). Now I know that one says 7-speed(the number of gears on the free wheel) and the other one says 21-speed ( the total number of gear combinations, 3 front X 7 back = 21 total), but they are the same thing. Either one of these is less than $20.00 less shipping.

I just recently did a replacement on my lady freind's bike and it was very simple. All of the information that you need is in the directions, including how to set up the brake levers for v-brakes or for cantelever brakes. The "new" set comes with cables and housings and is a pretty good deal as far as I am concerned. If you buy used shifters, you will probably need to replace this stuff. I tried messing around with the old shifters and nothing broought them back again. No soaking, lubing, or adjusting made them work right. BTW, try searching Shimano Altus Shifters on eBay. Leave off the "20".

Thank-you, everyone!!!

I really have to remember to set "instant email notification" for replies - heck, any notification would be better than thinking "I have not been notified of any replies; I wonder if I should go check that website...".

Thank-you, thank-you, thank-you.