I'm a solid supporter of the Sennheiser G3 Wireless Kits, but I do realize that starting from $600-$800+ they can be expensive for people just starting out. The reason you want a good wireless system is not only to be immune for other wireless interference, but you want a kit that can transmit a good full quality recording. Cheaper wireless kits often sound very thin or often referred to as 'tiny'. Sometimes just as bad as an old AM radio.
Audio-Technica has recently released a new 'System 10' Digital Wireless System available with a wireless body pack + lav, or wireless hand held mic (for ENG style). The wireless Lav system also comes with a Hot/Cold shoe tray for mounting the receiver and operates on a rechargeable Li-Ion battery (not sure if that's a good thing).
Operating on 2.4GHz with dual antennas to improve reception, these new kits are anywhere from $150-$220 dollars CHEAPER than the G3 systems, but only time will tell if they can perform up to par. For more information about this new kit check out the product page (click here).
Audio-Technica System 10 Wireless Mic System Lav or Handheld