Have a look at Mountain of Ink.

They have very nicely done images of ink both as a swatch and writing on various papers.

From someone relatively new to fountain pens here are my paper observations:

• Flexbook Adventure Notebook - 85gsm paper - Found to be very fountain pen friendly and tends to suck ink into the paper making it dry quickly making it good for fast writing with minimal to no bleed through.

• Leuchtturm 1917 - 80gsm paper - Nice to write on but ink is slow to dry and dark ink bleeds through (lighter inks may not be as noticeable).

• Moleskine - 70gsm paper - Not recommended for fountain pens, the paper bleeds through if you even breath near it, feels scratchy while writing and can cause feathering with certain inks. The paper would be good for pencils though.

• Rhodia - 80gsm paper - Nice paper to write on, has a slight scratchy texture that feels strange when first using it but you get used. Barely any bleed through with dark ink and dries pretty quickly.

• R by Rhodia - 90gsm paper - This is their premium paper and although it has the same features as the normal Rhodia 80gsm paper if you can get this version I recommend it.

• Clairefontaine Triomphe - 90 gsm paper - Very nice paper to write on though it's almost too smooth with little feedback from the paper.

• Midori - ??gsm paper - Haven't tried this paper yet.