HERE ARE SOME LINKS YOU WILL FIND USEFUL (and FUN)...
Simple sinewave synthesizer  SImple 16 step       sequencer...  You'll play with it for hours...  I       did...
Online Metronome  If you do not have a 
metronome, this one is free if you have
speakers...
eMusictheory.com.  Several good drills
and practice games for note reading and
rhythm, I especially like the "Rhythm
Performance" drill.  

Note Trainer - Good training for reading notes.  Go 
to Settings to change to your clef.

Big Ears is an online eartraining drill that will help 
you improve finding pitchs.  

Music Flash Cards.  A few different sets of flash
cards to help you with your note reading,
intervals, etc.

Classics For Kids.  Cool music stuff for students 
(and parents) including some radio show
schedules. And check out the GAMES and
HEAR THE MUSIC!

Drills, Practice, Downloads, Etc.
(Check back frequently...)
Here are some online practice drills, games, and other fun and useful stuff.
Finale NotePad - FREE NOTATION SOFTWARE!
Whenever I have to re-write a part for our band
or arrange a piece of music, I use Finale.  It
is an incredible program, and I find it
indispensable. NotePad is a free version  you
can experiment with to see what you can do. 
Write a song, arrange one you know...  Try it,
you'll like it!

Blank Music Paper - Need Staff Paper?  Guitar
Tablature paper?  Bass Tab paper?  You can
get it here...  just print it out.
Software and downloadable stuff...