I'm quite keen to give Flash Photography a try, but Canon's own gear is somewhat expensive!
I'm considering the Yongnuo range and in particular, the YN-568EX II. I'm also looking at the YN-622C radio triggers to accompany the flashguns(s). The fly in the ointment though, is the news that Yongnuo are rumoured to have a new flashgun on the horizon. That will be the YN-600EX-RT, very similar to Canon's own 600EX. This will have built in radio system which can be used with Yongnuo's new YN-E3-RT Speedlite Transmitter, which is already available.