My son is 9 months old and LOVES the Playskool Busy Ball Popper. It's about 17 dollars at Target. 5 colored balls go flying around.......he gets to pick them up and put them back in. (just a warning- in the beginning the game is "watch mom picks up these balls," but eventually they learn to do it.) Also- for a while he loved the Fisher Price Kicking Piano. I had that mounted to his changing table for a while and now crib. Nothing catches his attention like the Busy Ball Popper though...
Also- My son has a walker and loves it. I know the AAP says 'no walkers,' but I had one growing up and am fine. He gets to run around like crazy around the kitchen.... loves when I unload and load the dishwasher, etc... His new game is to chase his Daddy and me around the kitchen.
Before my son could be left sitting up I used to put the Boppy Pillow behind him to support him. Or- One of those armchair pillows (Walmart has them pretty cheap) that will support him behind his head and his sides.
We just went to a cousin's party and we loved a BIG red ball.... (Shoprite has them) It was huge! And- big legos for babies and a dancing spider man plush toy... Those will be my next coveted baby items.
Good luck! I completely understand your pain!
M. ;)