Well, nobody seems to have really assembled a list of what a server needs. I've been a server owner for some time now and I think I've gotten the hang of this stuff. I decided to assemble a list of what all the new server owners should try and install on their server (if they're running Bukkit, anyway). So without further ado, the list-

Essentials. You can't beat it. It has EVERYTHING a new server should want. Weather, item spawning, spawn location, teleportation, unlimited health mode, time control (ish), server rules, /help command, private messaging, admin viewing private messaging, warps, homes, jails, and some more fun and slightly useless stuff. It's pretty amazing. Takes four .jars to install, but probably the most useful you can have.
http://ess.khhq.net/wiki/Main_Page

MCBans. Global banning is always nice.
http://forums.bukkit.org/threads/admn-sec-web-mcbans-v3-1-complete-kick-ban-global-ban-system-1185.94/

BigBrother. Anti-Griefing is also always nice.
http://forums.bukkit.org/threads/sec-bigbrother-1-11-0-catch-griffers-red-handed-1060.12879/

CFBanner. Blocks a lot of stuff people use to cheat.
http://forums.bukkit.org/threads/admn-cfbanner-1-8-1a-get-rid-of-zombe-cjb-forever-blockface-approved-1185.27804/

WorldEdit. The greatest single plugin. Ever.
http://forums.bukkit.org/threads/edit-sec-admn-worldedit-4-6-world-editing-de-griefing-1000.62/

WorldGuard. Almost as good as WorldEdit.
http://forums.bukkit.org/threads/sec-worldguard-5-2-block-fire-ice-melt-mushrooms-advanced-fast-area-protect-blacklist-1000.790/

Regios. The best region protection around.
http://forums.bukkit.org/threads/admn-sec-regios-v4-0-71-advanced-region-management-multi-world-protection-more-1185.15898/

McMMO. Level and skill systems for players.
http://forums.bukkit.org/threads/rpg-mech-mcmmo-v1-1-16-rpg-addiction-redefined-multi-lingual-1185.3505/

Factions. If you want factions, use Factions. Pretty simple.
http://forums.bukkit.org/threads/sec-fun-factions-1-5-1-guilds-war-and-user-controlled-antigrief-1185.19063/

SimpleShop. Either a global shop, or my favorite use is as a limited item spawning system.
http://forums.bukkit.org/threads/sec-fun-factions-1-5-1-guilds-war-and-user-controlled-antigrief-1185.19063/

HeroicRebuke. An organized player warning system for admins.
http://forums.bukkit.org/threads/admn-heroicrebuke-v1-2-7-warn-players-and-track-warnings-211-1060.4237/

ClearInv. Very fancy admin inventory management.
http://forums.bukkit.org/threads/admn-gen-misc-clearinv-v1-8-0-selectively-clear-inventory-1185.21291/

FalseBook. Lots of fun mechanisms and stuff.
http://forums.bukkit.org/threads/mech-falsebook-0-88alpha-craftbook-for-bukkit-80-ics-cauldrons-gates-minecarts-1185.7227/

LWC. Chest and door protection at its finest.
ms.bukkit.org/threads/sec-mech-lwc-v3-53-lightweight-protection-for-chests-furnaces-dispensers-and-more-1185.967/

iConomy. An economy for your server. SimpleShop uses it, and so can a lot of other plugins.
http://forums.bukkit.org/threads/econ-iconomy-6-0-7-celty-1-8-1.40/

TimeShift. Time control however you think you might want it. Not quite updated but should still work.
http://forums.bukkit.org/threads/mech-fun-timeshift-2-0-1-change-time-on-the-fly-b953.1265/

So there you have it. All the most useful plugins for a new server owner. If you think I forgot something, leave a comment. Not that much of a hassle to update a blog.