Orkar Isber suggested translating the subtitles of Skyrim into Dovahzul. 
I will start working on this. This type of mod is easy to do when you ate waiting for something or have a bit of time to spare. Also, it may be one of the easiest mods to make, although it will take quite some time in total (depending on how good you are at Dovahzul ;) )
If more people feel like this is a good idea, then join in! We can coordinate who translates what so that we are not doing twice the work.

I translate all 'quests' which pop up with 'Generic' in the filter.

I wish to translate something for your mod. How do I do it?

I can make a small tutorial here. (If you never worked with creation kit, this should even be do-able) I don't know if you are (very) experienced with making mods, so I'll make it so everyone can follow. (also for others)

These steps are very basic, for people who never worked with the Creation Kit (CK)
First install creation kit. It should come with Skyrim and can be found in the Steam Library under 'Tools'.
1. Open creation kit.
2. Click 'File', then 'Data...' and tick the 'Skyrim.esm' box. Then click 'Ok'.
3. Say 'Yes to all' on all popups. If it crashes, search the internet (or ask here). Some errors occur a lot.

Now to editing the subtitles:
1. You won't need the render window or the cell view, so you can make the object window fill the whole screen. 
2. Click on the + before Character (in the object window) and then click on 'Quest' (just the word. The + shows different categorys of quests)
The quest tab holds a lot of information. Quests are obviously in it, but also dialogue is. (most) quests with a name (see the 'Name' column) are actual quests. 
3. Now you can use the filter (upper left of the object window) to search for specific things. The filter will look through the Editor ID's (first column). Generic dialogue often holds information which NPC's say when you are for example trespassing in their house. A few more things to search for:
CW = civil war
MQ = main questline
DB = dark brotherhood
TG = thievesguils
name of a city shows dialogue in that city
Follower = dialogue from followers
There are loads more, but this is a start.

Once you found a quest or dialogue that you want to translate:
1. Double-click the name or the yellow icon.
A window pops up.
Depending on the type of dialogue you opened, you may find the tekst in different places. I will discuss both using the DialogueGeneric editor ID.
2. First open the tab 'Dialogue View'. It has one editor ID, namely 'DialogueGenericView'. Click on that.
3. You now see some things in  the white space. You may have to move the blocks of text. You can do that by clicking on the orange bar and dragging the box around. 
If the box 'show all text' is ticked, it will (obviously) show all of the text. Some things will have text in the orange bar. This is something the player says. (I would not change that to Dovahzul ;) )
4. Double-click the orange bar which says 'OfferServicesTopic: What have you got for sale?'.
You will have a new window again. 
Now you see all of the possible replies, depending on the NPC.
5. Double click 'So you're interested in my potions and ingredients?'
6. Double click this sentence again in the new window (in the 'Response Text' box)
7. The text should be selected in the (again) new window. You can now translate it and retype the text. 
8. Once you're done, click 'Ok' on all windows (don't close them with the X, since that will not save the changes!)

Now we look at the other types of text.
This can be found in the tabs from 'Favor Dialogue' to 'Misc'. 
Since Favor Dialogue doesn't hold anything in this patricular 'quest', we go to the tab 'Detection'. 
1. Open the tab Detection
2. Select 'AlertToCombat' in the topics block. (middle one)
3. Double-click 'Now you're mine!' in the right block.
4. Double-click 'Now you're mine!' in the Response Text block and translate and retype it in the new window.
 

If you don't feel like making the actual mod, you can look up the text and translate it. If you give me the translation following the scheme below, then I can incorporate it into a mod.

EditorID: DialogueGeneric
Tab: Detection
Subtab: AlertToCombat
English text: Now you're mine!
Dovahzul translation: Nu hi los dii!

If you still have questions, let me know!

Thanks for the tutorial! Looks easy enough to follow, but this will change the subtitles in my copy of Skyrim, correct? Is there a way I could work on a different instance, an experimental workbench? And how do I eventually transfer the results to you?

Freymulaar

Thanks for the tutorial! Looks easy enough to follow, but this will change the subtitles in my copy of Skyrim, correct? Is there a way I could work on a different instance, an experimental workbench? And how do I eventually transfer the results to you?

You can always turn it on or off. When you save the mod, it will be automatically saved in the right folder, but it is most of the time not yet turned on.
To turn it on, you have 2 options (at least 2 I know):

With Nexus Mod Manager
- Open the Mod Manager
- Go to the tab 'Plugins' (top left)
- Search for the file you made (usually at the bottom) and tick the box.
You can turn it off by unticking the box. (With some mods, this may cause some trouble, but when you only translated the subtitles you're safe)

Witout Nexus Mod Manager:
- Start Skyrim through Steam (not with SKSE, if you use that)
- At the start-screen, choose 'Data Files' (so before starting the actual game)
- There you can also tick or untick the boxes of mods you want to turn on or off.

I am not sure how to merge mods. I think it's possible, and if not, we could have separate .esp files. (those are the mod files) The mod will be saved as an .esp, so you can just send that one if you translated something :)
The location of the .esp files is usually: 
C:\Program Files \Steam\SteamApps\common\Skyrim\Data
or
C:\Program Files (x86)\Steam\SteamApps\common\Skyrim\Data

Ah, what I forgot to say is that when you closed the Creation Kit and want to work on the same mod when re-opening it, you have to select your mod and click the 'set as active file' button in the bottom of the screen.