Last Friday Google officially announced what we thought for a while - that page download speed will be factored in to the rankings algorithms.  It is important to note that the official release and subsequent blogs from Matt Cutts have reinforced that it is only a minor factor compared to factors such as relevance and value-add.  The Google press release provides some good links to tools for assessing and improving download speed which you may find useful.  Whilst some people immediately think that the only option is to shift to a dedicated server which will cost more, there are also other tweaks to a site that can help and the tools listed by Google highlight them.  Google also push the fact that not only is download speed good for rankings, but will also improve user satisfaction and therefore help with conversions which has to be a good thing for site owners and users.