Wireless speakers. Now that the 30-pin connector is dead, seems like wireless speakers are going to be more and more important. If you just want a local solution then you can use Bluetooth adapters to connect any speaker set Belkin makes one for $25. Airplay actually works better because you can communicate on Wifi. We use this mainly with Airplay to Airport Express or to AppleTV or to any iDevice with Airfoil installed. The Logitech UE Air is a good example in that is supports Airplay (and has a 30-pin connector too). Or just use$99 AppleTV to an AVR with Optical input for a big stereo system.
So what do need as items for us...
High quality stereo. We have a high quality stereo amplifier (tubes, baby!). Interesting to hook up this so you can play from an iPhone. The ideal thing is an Airplay capable adapter. Could be an old iPod Touch always plugged in running Airfoil. Then you can play anything through the tube thing. Or get another Airport Express which acts as a convertor or an AppleTV does this as well with a TOSlink output but then needs a \$22 Toslink to analog RCA cables. So the cheapest thing to do is to find an old iPod Touch and use it. I've done this before with anything that has RCA analog inputs.