Do you do any ensembles? Small ensembles...like duets or trios? I sometimes give the kids a "duet day"...we take out some duet books, they pick some, work on them, then perform them. Or I'll play duets in a lesson, too.
SmartMusic is also a great and fun thing for them. There are many accompaniments, including some for many of the newer lesson books.
Something I tried last year, and will be doing again (albeit a bit refined...I really don't want to listen to 80 scales
) is a recording project where I assigned several scales and required rep (with choices) for the kids to record. You can use Audacity to great effect for this. Kids loved it and it gave them IMMEDIATE feedback on what they're doing.
We had one lesson where the kids had to play several scales by the end of the period. The reward: a handful of Gummi Bears! Man, 6th graders will go nuts if they think Gummi Bears are involved! They went ahead of me and did thirds, arpeggios (tonic and dom7) and chromatics!
Above all, have fun yourself, too. They are quite funny, little people, and can really brighten your day.
Oh dear...I just jumped in ahead of Ed. Sorry, Ed. I didn't see the little EC downloading text at the top of the page. (Jumped here from the "Recent Topics" part of the home page).