Lords of the Blog is a collaborative blog, written by a number of Peers from all parties (and none - the Convenor of the Crossbenchers, Baroness D'Souza is a regular contributor). By far the most active is Lord Norton of Louth - a Conservative Peer, but one held in high esteem for his knowledge of the British Parliament, legislatures in general and the British Constitution. If you have ever studied British Politics you are likely to have used at least one of the 28 books he has written. In the interests of full disclosure, he is my supervisor for my Ph.D.
Lord Toby Harris writes a blog - which is often updated many times a day. It is unashamedly partisan - he is a Labour Peer - but is one of the best sources (other than Hansard itself) about what has been dealt with in the thirty minute Question Time held on Mondays through Thursdays.