**** **** **** **** Notice - new dev version...

31Aug2010: If you're trying out Gmail's new [beta] Priority Inbox feature, then the dev version currently works with it (for me anyway). (FYI & FWIW, I won't be using Priority Inbox myself [beyond testing it for/with this style]; it's a pointless "feature" for me.) Alternatively, you could simply edit the source for this style and change ':nth-child(6)' to ':nth-child(7)' to allow for the extra buttons added by the feature.

22Aug2010: It seems Google has changed some things around on one of my accounts (but only one... so far, but everyone else can't be far behind)--had some more "children" apparently. Worse still, they move around from page to page (Inbox vs. search vs. wherever are different). Anyway, I'll have to see if I can't come up with a better [more "Google-proof"] way of displaying Google's Select menu in a "toolbar" format. The fact is, though, there are a hundred different ways for Google to break any "solution"--without even trying. Here's the new dev version if you want to use it: http://freestyler.ws/style/30390/gmail-a-little-retrofit.

On the other hand, you could setup a Quick Link with the 'in:anywhere is:unread' search term and use it with the 'Mark all as read' item in the 'More actions' menu (if your primary use of the Select list involves 'Select: Unread->Mark as read' clicking). Plus, the keyboard shortcuts still work [presuming you've enabled keyboard shortcuts in Settings]: type an '*' followed by 'a', 'n', 'r', 'u', 's', or 't' (so, the first letter for each [except for 'unstarred']).
**** **** **** ****

* * * * * * * *
Options that are, by default, disabled are structured like this:

/* description of option *[off]/
.
. (code)
.
/**/

To enable an option that is off, you simply remove the '[off]' from between the asterisk and the slash, thereby closing the comment for the option's description. (Enabled options have a similar structure, only reversed. To disable an option that is enabled--one with '[on]*/' trailing the description, put one or more characters between the asterisk and slash. I use '[on]' and '[off]' simply as pseudo-self-documenting eye-catchers.)

* * * * * * * *
This style works in Google Chrome now mostly the same way it does in Firefox.

* For the "real" Contacts manager, use "https://mail.google.com/mail/contacts/ui/ContactManager".

** See http://freestyler.ws/style/30226/gmail-color-the-compose-mail-button for something a bit more elaborate, as well as code to set the background color of the Select links on hover (to match the Compose mail button if desired).

*** NOTE *** By default, the colors in this style are designed to work with the Planets theme (or any dark theme). If you're using a theme with a light background, then you'll likely need to change the text color from white to something darker--see the comments in the code for some help there (or post a question below).

Development...
20Aug2010: definitely need to normalize the code--too much top/bottom duplication (no hurry, though)
16Aug2010: I've got a second style ready which restores the Select links at the bottom of the list--useful for those who opt for the higher 'Maximum page size' settings; need to do some code clean-up for both before posting it; will add some code/comments related to changing the colors of the links as well as the buttons. Here's a "preview" with some options enabled:
http://a.imageshack.us/img594/5238/gmailselectlinksbothpre.png

Updates...
20Aug2010: for the Compose mail button as a link option make the cursor a pointer on hover
19Aug2010: correct the "hide the button part entirely (show just the check box)" option
18Aug2010: added links at bottom, works same way in Chrome, added some other options (see above)
15Aug2010: Google Chrome-/WebKit-related tweaks (box shadow off, border radius on)--sorry, not using Chrome much these days. (Sorry, again, but WebKit doesn't work the same way as Gecko, so the layout in Chrome doesn't look the same as in Firefox--can't really help that in this style [which is for Firefox and Gecko], beyond adding the CSS which doesn't conflict with Gecko. I might simply create an extension specifically for Chrome, if anyone wants that [or, for now, you can try out http://freestyler.ws/style/30069/gmail-select-links-restored-for-chrome ...if you want].)