Thank you for doing....

[KeithH]

I know how to say thank you, of course. But, how do you thank someone for doing something specific for you?

"Thank you for helping me."
or
"Thank you for listening to me."
or
"Thank you for loaning me $5,000,000." (I need this one often)

...thanks!

[Solvi]

Several of my Japanese pen friends say メールありがとう, so that probably applies to other objects as well (please let me know whether I'm right or wrong on this). I haven't got a clue about actions though.

[Bueller_007]

Yes. You can just say Nounをありがとう. (The particle often gets dropped.)
Or instead Verb.te-formありがとう.

[KeithH]

そうですか？SolviさんとBuellerさんは教えてありがとう！

[Bucko]

Might be better to use the て form plus くれて etc.

教えてくれてありがとうございます。

This gives more of an impression that a favour was done.

[tiroth2]

You'll want to use 教えてあげて for teachers, since くれる is for someone on the same level as you.

[Bucko]

You'll want to use 教えてあげて for teachers, since くれる is for someone on the same level as you.

What do you mean here tiroth2? 私に教えてあげて is grammatically incorrect as far as I know. When you (or someone in your group) receives something, you use くれる for 'give'. Both くれる and あげる mean 'give', it just depends on the who the receiver is.

If you want to be more polite (like with a teacher) you'd say something like 教えってくださってありがとうございます。

Please correct me if I'm wrong.

[Jason]

教えてくださって is correct here. Or if you want to be even politer:

教えていただいて感謝です。