Hey guys, I'm about 8 hours into Mass Effect 2 and I'm loving it. I'm playing as a male Shepard(who chose a relationship with Ashley in ME1) and I wanted to know who you can bang and if you can bang several characters.

No you cannot, you have to chose, also Bigamy is having more then one wife, you cannot get married in ME2, it would just be cheating

Actually, you can get with as many as you want...just have to wait for after the end and make sure they're still there.  Also, you can't have gotten with them before and moved on, they won't take you back once you've shut them out.
 
To answer the first question:

Given the way Liara was treating me, I never thought of it as "cheating" on her, until I realized what she had done for Shepard long after it was too late.

"Actually, you can get with as many as you want...just have to wait for after the end and make sure they're still there.  Also, you can't have gotten with them before and moved on, they won't take you back once you've shut them out.
 
To answer the first question:

SPOILER WARNING: Click here to reveal hidden content.

Miranda Lawson,  Tali'Zorah nar Rayya, Subject Zero, and Morinth. 

SPOILER WARNING: Click here to reveal hidden content.

Though, with that last one you die and have to reload...

"

Can you not post spoiler material under General Discussion?

I hit Jack and Miranda on my playthrough. Playa? I think so

"I hit Jack and Miranda on my playthrough. Playa? I think so "

Gotta roll fem Shepard. Best romance plots in the game are

When you have the chance, you should choose Morinth.  She's the only one you get to see nude.  So get at it, son!

" Can you not post spoiler material under General Discussion? "

I thought they fixed it?
@Lies said:

" @Lind_L_Taylor said:

" Can you not post spoiler material under General Discussion? "

Everything's getting posted to general discussion atm due to a forum bug "

There might eventually be a mod on the PC version.  There is a polygamy mod for Dragon Age: Origins out now, so perhaps given time the Mass Effect 2 community will delve into the code and create something.  Of course, I think the interconnecting character storyline is much tighter in ME2 than DA:O, so it might be more difficult.  Additionally, having more than one relationship would confuse things with a ME2 to ME3 import.