hi,
for transport, the place to look is the Transport for London website as this gives not only info related to the carnival, bit also any other problems on the network that may affect the weekend. For example, here's their info for last year which has everything you need to know.
http://www.tfl.gov.uk/co...ntre/archive/12382.aspx
So check this nearer the time for 2010 info.
Concert info would not be available too far in advance - there's nothing around at the moment I don't think. You will have to just search the web nearer the time - events tend to get published on lots of independent websites rather than in one central listing. The advice of this ex-Ladbroke Grove resident is just find a nice place to hang out and let it all happen around you!