These are a few websites that every Gundam fan will find useful.

 

GundamInfo
Mecha and Anime Headquarters (MAHQ)
Dalong’s photo reviews
Gundam Guy (News)
Hayamimi Gunpla Information Station (Japanese news)
Gundam Eclipse forums
Gundam Wiki
Ghostychan’s Gunpla Blog
Reddit’s Gunpla forum
OpenHappy gunpla and cosplay
Project Gunpla

 
Some great stuff on youtube:
GundamInfo
2old4toys
Vegeta8259
Zversus
PatrickGrade
ArvinAngeles

More to come…