Instructions:
You may want to change a few settings to make the style fit the size of your monitor. Look for the following in the code and change the large numbers to whatever looks best on your monitor.

/* Changes height of email list and makes it scrollable */
div[class='Cp nH oy8Mbf']
{
overflow-y: scroll !important;
overflow-x: hidden !important;
height: 613px !important;
}

/* Repositions email list */
div:first-child+div[class='nH if'] div:first-child+div[class='nH'] div[class^='nH hx']
{
position: relative !important;
top: -6px !important;
width: 956px !important;
}

/* Prevents extra scrollbar from appearing due to message height */
iframe[class='d4 d3 editable'] { height: 500px !important; }

/* Repositions conversation text boxes */
div[class='ii gt']
{
position: relative !important;
top: 0px !important;
left: 0px !important;
width: 914px !important;
}

I've included some brief notes in the code, in case you want to change something. This style won't suit everyone's needs, but for those who may find it useful, enjoy.


Updates:
2/11/10 -- Made a couple of minor changes including removing the blue font hovering affect from the Move To, Labels, and More Actions buttons.
2/17/10 -- Removed "About these links"
4/26/10 -- Updated to address recent Google code changes
4/27/10 -- Small fix for multi-login script box
6/6/10 -- Fixed the "Map This", "Add to Calendar" box that sometimes appears on the right hand side of conversations.
6/23/10 -- Fixed the above box again
7/14/10 -- Adjusted the script for having the attachments display on the left hand side of the email list (see Gmail Labs), which I prefer
7/30/10 -- Further fixes to the "Map This", "Add to Calendar" box that sometimes appears on the right hand side of conversations.
8/13/10 -- Made adjustments to style to accommodate changes made by Google and Gmail Redesigned
8/14/10 -- Made a couple minor adjustments
8/16/10 -- Made some adjustments to the Google Calendar widget and for the new Boomerang add-on
9/9/10 -- Removed stars again from Inbox due to coding changes
9/10/10 -- Made some adjustment to accommodate Daniel Slaughter's GMail POP3 Checker (http://www.danielslaughter.com/projects/gmail-pop3-checker-for-greasemonkey)
1/28/11 -- Made some adjustments based on new version of Gmail Redesigned
1/31/11 -- Fixed reply button
2/7/11 -- Some minor tweaks. Restored Refresh button. Changed style of top button toolbar.
2/21/11 -- Fixed position of Reply buttons
2/27/11 -- Fixed position of navigation bar and turn off highlighting button
4/2/11 -- Made a number of small adjustments to address Google coding changes and remove imperfections
4/19/11 -- Addressed some Google coding changes
4/21/11 -- Fixed broken elements