Everyone's giving you alternatives to WMC. If you're asking about alternative guide listing providers that you can use with your existing WMC, then off the top of my head I can only think of three:
- EPG123 by garyan2 (Free but you need a $25 per year subscription from Schedules Direct, SUPER reliable, easily configurable)
- EPG Collector (Free, somewhat reliable, decently configurable but tedious) [See this post]
- zap2xml - Uses either the Zap2it or TV Guide listings (Free, pretty reliable, highly configurable but you need to stay on top of it)
If this wasn't what you were asking about, please accept my apologies!