http://www.spaceweather.com/ Watch the sun
http://www.solarcycle24.com/ another good resource for solar activity
http://www.coaa.co.uk/beaconsee.htm beacon software
http://www.dxinfocentre.com/tropo_eur.html great for tropo openings
http://dx.qsl.net/propagation/
http://pskreporter.info/
http://www.arrl.org/propagation