Rails - the Jolly Jumpers (the things that hang in the doorway) are great. Babies tend to love them. My MCHN warned against using them too much tho. As with baby walkers (which they advise against altogether), they can hinder the child's natural development from laying on the floor to crawling. They need to spend lots of time on the floor just figuring out how to get things working and moving.
Have you tried having nappy-off time? Gabby just loves having her nappy off and spends ages every day just laying on the floor with a bare bum. Every time I change her nappy I let her have a play with it off. I just put a cloth nappy or a towel under her to stop her from weeing all over the floor. She plays much better with it off and will even roll every now and then a lot better with it off.
With toys, I attach a few "Link-a-doos" to them so that she can get a better grip. She tends to drop toys and not be able to pick them up but the link-a-doos (like plastic chain pieces) help her to be able to pick them up again.
Gabby did go through a stage where she didn't play very well for very long but she snapped out of it eventually. Hopefully your baby will too!
HTH!!