how to phrase 'thank you for...'.

[ggenglish]

An expression i usually use in english would be to say 'Thank you for <action>'.

What's the best way to do this in japanese?

My vocab is week so best i can muster up is:
Thank you for your e-mail.
あなたのメール、ありがとう。
このメール、ありがとう。

Is there a alternative/better way to do it? My example is not good because the <action> part is short. What if it was a longer english sentence. (i.e. Thank you for taking the time to read this post and provide such a nice example. ;-D )

Seriously, Thank you. hehe.

[chinz]

I would say,
メールを読んで、ありがとう。
Thanks for reading my mail.

If it's an action done for me,

手伝ってくれて、ありがとう。
Thanks for helping me.

[Javizy]

メール/返事、ありがとう works okay as far as I know, but as chinz said, if you're thanking somebody for an action you use the て-form (usually followed by くれて・くださって) followed by an expression of thanks ありがとう(ございます), 感謝します, or something like that.

来てくれてありがとう。
Thanks for coming.
温かくもてなしてくださってまことにありがとうございました。
Thank you ever so much for the warm welcome.

[ggenglish]

cool. exactly the replies i was looking for. I haven't practiced -te that much but hopefully this works:

答えてくださって本当にありがとうございました!

thank you both!

[Belton]

Just on the specifics of thanking someone for an email or a letter.
お返事、ありがとう
is the one I've come across the most as an opener. "Thank you for your reply."

[Taurus]

On a slightly related note, when I thank people in English for doing something nice, I tend to do so by saying 'you're so kind! Thank you so much!' (complete with exclams). I kept trying to translate that literally into Japanese by saying something like 'shinsetsu desu! Arigatou' or whatever, but my mother-in-law said it sounded unnatural and came up with 'go-shinsetsu ni arigatou gozaimasu' as the best way of conveying a similar sentiment.

(Which, as an aside, is one of the reasons why I think it's better to learn Japanese by translating from sample sentences, rather than learning some grammar rules and trying to translate literally.)