I'm not exactly sure what you mean by "tail". You can change the logfile options to start a new one each day, each week etc. That way, you can control the size of your logfiles, depending on use.
As far as log file analyzers go, I'd recommend two. Web Trends makes a good one (webtrends.com), it can be used for both proxy logs and normal web logs. It's sort of generic when it comes to proxy logs.. works good though. The other one I'd recommend is Webspy (webspy.com). It's very specific to proxy logs and gives alot of "canned" reports. It is very good and very specific.
Hope this helps.