well... in the full orchestra there's a ton of strings mainly violins, violas, cellos, we had a bass at one point, and a harpist at one point too; in woodwinds we have clarinets, saxophones(i dont know why), oboes(one being me), flutes/piccolo; brass has trumpets, french horns, trombones and we have no tuba. well, our conductor sometimes plays it but its extremely rare. the instrumentation differs in each orchestra, such as there could be more instruments in another orchestra that i didn't mention, but those are basic orchestra instruments.
Strings, oboe (w/english horn), clarinet, bass clarinet, flute (w/piccolo), french horn, trumpet, trombone, baritone, tuba, percussion, and piano. I think I covered it all; I don't usually see saxophones in orchestra.
Almost always, there is Strings, Flute, Oboe, Clarinet, Bassoon, Horn, Trumpets, and Timpani, but most pieces (especially once you get past baroque and classical) also call for trombones, various percussion instruments, tuba sometimes. Pieces may call for English Horn and Bass Clarinet also, and very very rarely, Saxophone and/or Euphonium.