How do I put mods on my minecraft server? [duplicate]

I know how to set a Minecraft server and I already know about plugins, but how do I install mods on it?

For example; Deathchest, Pokemobs, Mo' Creatures, Recipe Book, TooManyItems, and all the things necessary to make them run.

I've looked everywhere. Finmine wont give out how they set their servers up with mods but they have Mo' Creatures and ComputerCraft and some others. I only found a custom thing needed to play on their server.

Is this related to the version I'm running? If i have to downgrade my Minecraft from 1.2.5 this isn't a problem.

You would need to get something like Bukkit. Then, you put whatever plugin.jar into the plugins folder at the root of your main server directory. You could get Bukkit-compatible plugins at dev.bukkit.org

However, there are most likely not going to be mods that add an User Interface or more blocks.

You have to put the mod files in the minecraft_server.jar file But dont delete the meta-inf and if it says in the mod thread that you need modloadermp than search modloadermp server i think this would help

To do basic mods in SMP, you'll need to have the server version of the mod, and it is necessary that all clients have the client versions of all the mods you'll have loaded on your server. Installing them is pretty much the same as getting mods on Single-player. Bukkit works, and a friend of mine has gotten vanilla mods (Flan's Mods/etc) to work with bukkit. The only problem with that is you'll have to designate ALL ID'S yourself and make sure none are overlapping.

If you're using Bukkit, I've never used it personally, but if I recall watching my friend do it correctly, all he did was move the files into a bukkit .jar file - whichever is the main file (e.g. Minecraft's is minecraft.jar).