So I'm about to start ME1 again as I just got ME2 (late to the party I know) and was wondering what DLC of the first game effects stuff in the second one. 
This only because I'm I like to explore everything the game has to offer and I'm pretty OCD about this stuff.

Neither really. Pinnacle Station never comes up again, and for Bring Down the Sky, you end up maybe getting an email, depending on the choice you make at the end.
 
If I remember correctly, both might have "News Announcements" associated with them (when you select a News Terminal).

Screw Pinnacle Station unless you want chieves. That one is basically just an arena thing. The only thing that would be of interest is Bring Down the Sky that, while not affecting the sequel, does add some story to the Batarians.

I haven't played mass effect in a long time, so when you say new announcements do you mean in game or real new announcements like if they affect ME3?

Thanks now I can spend more money on ME2 DLC than ME1 DLC which can never be a bad thing really