For a listing of linux-related Mailing Lists, peruse websites such as the Linux Resource Exchange and the Linux Online Mailing Lists
A relatively new, excellent Mailing List resource is Geocrawler (The Knowledge Archive). This is a continuously updated, searchable archive of a large number of Lists that also allows one to register and subsequently post to any particular Mailing List. Its user interface is simple and its search function delivers messages very quickly. I highly recommend this site.
You may also find Mailing List archives at the following locations :
The website of the distribution of Linux you use.
The website of the Window Manager or Desktop Environment you use.
The website dedicated to the application or project in question.
This is not a complete listing of archives and you may find additional sites with an Internet search engine. But, this should certainly get you going.