where can I find reliable conversion tables from U.S. measurements to metric measurements for baking and cooking?

Seajambon:
.....There has also been at least one severe recipe failure on this site where a UK Food52-er didn't realize the flour difference, used a US based recipe....

I am in the UK and unaware of the 'flour difference', can you please elaborate!!

In addition to properly converting measurements, there may be some issues with ingredients (for example, wheat flour is not exactly the same around the world and you can have some tragic results if the recipe calls for "all purpose flour" and you use something that seems like it should be the same but actually isn't as it may have leaveners added). I'm not sure how you can check but heard an interesting story about Rose Berenbaum having to fully rework her wonderful "Cake Bible" recipes before the book could be released in the UK due to the differences in the ingredients (especially flour). There has also been at least one severe recipe failure on this site where a UK Food52-er didn't realize the flour difference, used a US based recipe, and had unfortunate cupcake results. Finally, due to the altitude in much of Peru, be sure to make any "high altitude" adjustments that are required.

Having said all that - I LOVE how international this site is! What a lovely treat to know that folks from all around the world are participating.

I found (and copied for my own reference use) good tables at The Metric Kitchen:
http://www.jsward.com/cooking/conversion.shtml

Conversion lite. Free app. I love it!

My daughter the baker insists the best way to measure when cooking and baking is by weight. She made sure I purchased a scale that measures both ounces and grams. Highly recommend purchasing a scale. They don't take up a lot of room. This is the one I have http://www.amazon.com/OXO-Grips-Stainless-Pull-Out-Display/dp/B000WJMTNA/ref=sr_1_6?ie=UTF8&qid=1336377276&sr=8-6

Just use Google. Type the conversion you want into the Google search bar and it will return the answer. For example, typing "15 ounces in grams" will return the result 425. Works for all sorts of measurements. By the way, just tried a pound of Peruvian coffee for the first time--"Kikira" from the southern Puno region--delicious!

Google