Standard wall wart capability
 

Can the basic wall wart that comes with radio systems charge NiMh packs? Or do they need a special charger?

Also, I was told by a club member that turning on my RX and TX and leaving them that way is an OK way of discharging my Nicds. Any truth to that?

Standard wall wart capability
 

Yes, and no.

The wallwart is fine to charge a NiMH pack as long as you know your remaining capacity. If it's a bigger pack(I run 1650 nimh in both Tx and Rx's) you'd be charging at such a low rate that it'd be difficult to damage the pack. I always use my wallwart for a first slow charge on a new NiMH pack. Dave Thacker at Radicalrc.com has some good info on figuring out how long you need to charge at a given mah rate.
Don't discharge your pack using your Rx and Tx. This can leave the packs unbalanced as well as potentially damage your Tx and other radio equipment. Never leave your Tx on for a long period with the antenna collapsed either. if you're using NiMH there is no real reason to discharge them unless you're going to check their capacity. I never have discharged mine and after a few years, they're still going strong.