DreamHost recommends 500-1000 emails per hour.  I'm making contact with them again regarding their policy.  From their previous replies, they state that they route ALL email from ALL servers through a single point, and this is the reason large ListMail queues slow things down for other users.  I am trying to get them to be more supportive of list email because they are such a decent host - am actually awaiting a new reply from tech support.
If you have a reasonable list under 10,000 I still recommend DreamHost and will do a free install if you sign up as my 
referral.
Alternately, there's space on one of my own email-friendly dedicated servers starting at $15/mo for under 10,000 users.  
Email me if you're interested.
Regards