Check out other people's trade threads. Many people offer event pokemon which you can obtain by trading with them.
SoulSilver: Friend Code- 1549 4691 2103
White2: Friend Code- 2366 8235 3267
X: Friend Code- 4313 0591 6738
Time Zone- -5 GMT
Check out my Trade Thread: Fallen's Trade Center Gen4 and Gen5
I sprite a little on my free time, check it out: Fallen's Art Gallery