Ok, this isn't WP7 relevant, but...

[J4rrod]

How do I see what threads I've participated in on these forums? I can't find anything that says "My Forums" or anything.

 

[foosball]

You can click on your public profile and check your stats. From there you can click on your posts.

 

[palandri]

Click on your name and select find more post by J4rrod