How large of a sdhc would I need for a Nikon D3100?

How large of a sdhc would I need for a Nikon D3100?

Depends on:
-The quality you will be shooting (JPG fine/norm/low vs. RAW)
-Number of photos you will take at a time

Usually a 4GB or 8GB card works.

Since the 3100 does HD video like my eos t1i, I'd suggest an 8gb class 10. Class 10 is the fastest SD HC card there's at the moment so you won't have any lag recording videos to it. Mine are done
in a flash, even after running for 2 or 3 minutes. You'll like the class 10

4 or 8GB, with Class 6 and higher.

You can get them from $10 and above, all perform 99% the same.

Here's a guide on buying one - http://www.the-dslr-photographer.com/2010/05/canon-ef-50mm-f18-ii-review.html

I would consider SanDisk 8GB Extreme SDHC Class 10 High Performance Memory Card (SDSDX3-008G-P31)

Fast speeds of up to 30MB/second - CLASS 10
Offload photo/video content at record rates
Maximizes you camera's continuous shooting abilities
Designed to perform in the most extreme conditions
Includes FREE RescuePRO Data Recovery Software Download Offer