My dd is 21 months; we go out somewhere every morning (toddler group, friends' houses, soft play, swimming etc) then she has lunch and nap and then I have to keep her occupied for a couple of hours till tea time. Then the telly goes on till dh comes home. I find she doesn't sit immobile and stare at the tv for more than about 10 minutes, then she is running round, playing with toys and looking at the tv now and then, so I don't worry about it being on for more than 30 minutes.
Some ideas though -
Rotate his toys (one box downstairs, one box hidden in a cupboard, swap every 2 weeks) - so they are new and interesting.
Put a washing-up bowl with a couple of inches of water on a towel on the kitchen floor with cups, sieve etc to play with (be prepared to mop up and change all his clothes afterwards)
Strip him naked and let him stand in the bath and play with the cold tap and a cup / watering can
DD likes to follow me around while I'm cleaning - has her own brush and duster (is that just a girl thing?)
Playdough - it is ok if it goes in his mouth as long as he doesn't eat the entire tub
chalks and a little blackboard/slate (Woolworths do them)
put lots of pillows / a duvet next to the sofa so he can jump off the sofa onto them
find some more toddler groups to go to
get a little trike or ride-on for him to trundle around the house on
dd likes "dressing up" - I have a bag full of different hats
also likes to be given a bag or potatoes / carrots etc, a saucepan, colander, wooden spoon, a few plastic bowls. Then she 'cooks' and serves meals to her teddies
she likes to type on my computer (open a Word document and set the font size to very big and make it bright red, then make Word full screen)
dancing to nursery rhyme cds (or my music for that matter)
blowing bubbles
if she is very boisterous I chase her round the house for a while
HTH!