I've been getting lots of questions about paper and what to use for a specific project...so, since you asked, here we go! These are my opinions and what I think works best. There are lots and lots of choices out there, this is just to provide some direction. Whenever possible skip past Michael's and AC Moore and support your local independent retailer, please?
Okay, to be fair, you can stamp on anything. That said, the quality of your results will be reflective of the quality of the paper you’ve stamped and colored on.
65 lb "cover stock": light weight, cannot be turned over to use the other side when you’ve made a booboo as it will show through. This is generally the weight sold in packages by AC Moore and Michael’s. I don’t recommend this weight if you are going to color with any type of markers or using any water based coloring products. Fine for coloring with colored pencils.
80lb "card stock": Can be purchased by the sheet at your local stamping store. Look for bright, smooth paper. Neenah Classic Crest, Solar White is the paper of choice for many folks. Takes all coloring media well. Sells for about $26 for 250 sheet ream.
110lb card stock: My preferred choice for all around stamping. Papertrey Ink sells 100 sheets for $12 online. This is ultra smooth, bright white (or ivory) and does not pill when using loads of color such as copic markers or watercolors. I am not aware of any local stores that carry this stock.
Glossy Stock: generally 65# or 80#. Remember to use the proper ink (see December 2008 ink posting). Expands your range of direct to paper techniques.
Vellum: Many weights. I like a heavier weight, again ink choice is important. You can emboss on vellum, don’t believe those who say you can’t! Generally you’ll color your images from the back on vellum.
Parchment: Excellent for embossing and then using water based markers (Tombow, Marvy) to "paint" with a wet brush. A package of 10 sheets should run about $3.50 at your local store.
Ultra RS: This is sold by Judikins (www.judikins.com) it is very smooth, no tooth, bright white and comes in postcard sized pads. Takes all inks and coloring products well.
MatteKote: Also sold by Judikins. This is a clay coated paper that should be used with dye inks for best results. Takes the Tattered Angels Glimmer Mists well. Also sold in postcard sized pads it is acid free and archival quality.
Acetate or plastic: remember to stamp with solvent based ink (StazOn) and color from the reverse side.
Watercolor paper: Ah....my real love! Buy the best quality you can afford, it will show in your end result. I like 140#, cold press, paper. This has a medium tooth, takes lots of water without pilling or curling and has a great "heft" to it. Usually not carried by local stamping stores, this is a good thing to use that Michael's coupon on! Arches os a lovely brand. Try this with your spray water colors, Glimmer Mists, Twinkling H2O, etc. You'll LOVE the result. Remember to really ink up your stamp with india ink or a pigment ink, let it dry well or heat set, then go to town.