The 'other' instruments include: harp, piano, organ, harmonium, harpsichord, fretted strings (guitar, banjo, etc), accordion, voices, chorus, recorders, electronic instruments, tape and digital sound!
Plainly each one of these could have an online manual of its own. In many cases, a thorough study of pieces which have used these instruments will help, but electronic, tape and digital instruments still represent relatively uncharted territory in orchestral music.
Of the instruments listed above, the harp is probably the most common addition to the orchestra. 19th Century music often includes vocal and keyboard parts, and the harpsichord is particularly associated with Baroque and early Classical orchestras.
Use the menu above to sample various scorings from the Philharmonia's recorded archive.