How do I escape the Far Lands?

Try using NBTEdit to edit your location. Assuming you're running the multiplayer server, the file will be located here:

server/world/players/YourName.dat

...where server and world are the folders the Minecraft server and world files are in, respectively. If you aren't running it, you'll have to ask the administrator to fix it for you, though.

It may be a good idea to look at other player data and set your coordinates to the same as theirs.

Note that I'm not sure if this will actually work, though; I'm going off the assumption that the player dat files are just per-player NBT files, and NBTEdit is fairly old.

Here's the link to NBTEdit: http://www.minecraftforum.net/topic/6661-nbtedit/

I'm assuming that you're on multiplayer, so contact the sever owner and get them to delete your .dat file, this will reset you to the public spawn point of the server, you will lose all your items and maybe privileges and attributed area (depending on the mods) from doing this however, so this is a last resort (after asking them if they can edit it).

If you have a friend who can teleport other players (on vanilla servers, that means being an op and using /tp <PlayerToMove> <DestinationPlayer>), they can type in the teleport command ahead of time and hit Enter as soon as they see you log in. This will update your position on the server even if you lag out again; you'd simply be back in familiar territory once you logged back in afterward.

Since you own the server

I have to reset the server

then copy your .dat file located in server/YourWorld/players/YourName.dat, paste it as a copy, and then delete your dat. Make a new .dat file with INVedit, enter your items one by one (the reason you saved a copy is to EXACTLY enter the stats as your previous), and then save it as "your username".dat (without the quotes) in server/YourYorld/players/YourName.dat. Then you can delete your copy. When you go back to your server, you'll be in the spawn point.
_{BTW, going to the Far Lands is a really nice job. If you went there legally (no server commands), that's pretty good!}