The websites that are the most useful for updates on space weather conditions are as follows:

 

NOAA Space Weather Center - This is a major, and official, source for space weather warnings and data about the current conditions using satellite and ground-based data

Spaceweather.com - This resource gives you a popularized synopsis of the current space weather conditions. It includes amateur photos of aurora, and stories related to the latest solar storm event.

International Space Environment Services - The international version of NOAA's Space Environment Center.

NASA Spacewarn Bulletin - Updates on satellites, launches, orbit decays.

The Space Weather Journal - The American Geophysical Union has created a journal for space weather researchers to publish their findings.

IPS Radio and Space Services - The Australian space weather service, with a particular emphasis on radio interference issues caused by solar flares.

Student Observation Network - A great page featuring links to dozens of online satellite and ground-based real-time data sources.