http://www.startssl.com/ will give you a free SSL cert.
They've got a "How to install" section that specifically deals with Apache (and another one which deals with WHM/cPanel if you're using that for your LAMP management).
It's less than an afternoon's work to get up to speed.
Note that you'll need a dedicated ip address (or you might settle for a server running new enough versions of Apache to use SNI - http://wiki.apache.org/httpd/NameBasedSSLVHostsWithSNI - but that'll still not work for IE6 and very old versions of other browsers - pre 2.0 for Firefox)
