Here are some Twitter Stats culled from Tweetstats.com and Twitter Counter.com. Please note that most of the data is from Tweetstats and I note the TwitterCounter stats, which essentially notes the Twitter popularity ranking for that particular politician.
@M_Ignatieff 5,515 (via TwitterCounter.com)
400 tweets, 9700 following, 80k plus followers
1.2 tweets per day and 13 per month on average from Nov 2008 through March 2011.
Can follow him in Franch at @Ignatieff_M
5349 Tweets, 500 plus following, 3 plus followers
@pmharper 3,496the top twitter user (via TwitterCounter.com)
340 tweets, 12k plus following, 117k plus followers
Harper averages 1.6 tweets daily and 11 per month from July 2008 through March 2011.
@jacklayton 6,250 (via TwitterCounter.com)
847 tweets, 11k plus following, 71k plus followers
On average, Layton tweets 1.9 times per day and about 26 tweets per month from July 2008 through March 2011 (Tweetstats).
@elizabethmay 25,509 (via TwitterCounter.com)
838 tweets, 4K+ following, 16+ followers
She tweets 2.6 times per day and 26 tweets on average between Sept 2008 and March 2011.
Also has a French account @mayelizabetth with 169 tweets, 268 following, and 392 followers.
@GillesDuceppe 9,169 (via TwitterCounter.com)
437 tweets, 7K plus following, 50k plus followers
Duceppe averages 1.8 tweets per day and 15 per month from roughly July 2008 through March 2011.