Are you saying you want to be able to open one form and simultaneously add
items to different lists?

I'm not sure you want to design it that way.

Yes, thats what im saying, basically like using custom lists as a database with
a single front end.

the other thing i could try is to have a single list and if you choose field 1
option A, fields 5 6 and 7 show up, if you choose field 1 option B fields 2 3
and 4 show up. no idea how to do that though :)

what im looking to do is a network inventory that i'd like centralized so you
can easily display, for example, whats in room 1 rack 1, or whats on subnet
x,y,z but because there will end up being a lot of fields because of the vast
number of different device types i figured it might be easier to create
different lists for these and then design a form.

what do you guys suggest?

1. Content Types or,

2. jQuery the NewForm.aspx

There may be other suggestions....

Content types are limited to a single list. JQuery is possible, but it would be
difficult since the new form by default is for a single list. I suspect that
custom coding would be the only way. But the question then is why do it at all.
SharePoint is not a relational database. If you need an RDBMS then you would be
better off putting the data in something like SQL and writing custom web parts
or using BCS to access the data.

Thanks for the responses guys. It looks like i can pull this off with content
types.

Im not really against writing a web part for this, but i wanted to take the path
of least resistance. Sounds like a webpart might be the best way to do this in
the end because chances are, once i get started, i'll want it to do more.

If you're just concerned about accommodating different data field
combinations for different items, then I'd suggest creating a Content Type
for each one. You can keep them in one list, and SharePoint will take care
of generating the form as appropriate.

You can use the Content Query Web Part (CQWP) to aggregate information from
multiple lists into one view/output similar to a database join. Google
Content Query Web Part and you'll find a ton of tutorials.

As for doing the data entry into multiple lists on a single form, I can't
think of any way to do that without some compiled code on the server.