This excerpt was taken from Wikipedia regarding Discover Card acceptance:

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In Canada, Discover brand cards are accepted at few locations, usually at businesses catering to American tourists, such as car rental agencies and hotels, as well as major American merchants like Sears and Wal-Mart. Some Canadian businesses do accept Discover cards but opt to favor Visa, Mastercard, American Express and Interac. ATM service offered by Discover is not currently available in Canada, although cardmembers apparently could access cash at any Sears Canada store. [2]
In the United Kingdom, Discover issued credit cards on the MasterCard network under both the Goldfish and Morgan Stanley brands [3]. This division was purchased from Lloyds TSB in 2005. It was subsequently sold to Barclays on February 7, 2008. These cards have since been rebranded as Barclaycard Goldfish and Barclaycard Platinum respectively.
While Discover brand cards are not currently accepted in Europe, the company's presence continues to grow in Mexico, Costa Rica, Micronesia, the Marshall Islands, Belize, Palau, and many of the Caribbean Island nations. The corporate web site FAQ section http://www.discovercard.com/customer-service/faq/international.html describes specifically where the Discover Card is accepted outside the United States.
Additionally, in May 2005 Discover Network announced an alliance with China UnionPay Network. The two companies have signed a long-term agreement that will lead to acceptance of Discover Network brand cards at UnionPay ATMs and point-of-sale terminals in China and acceptance of China UnionPay cards on the PULSE network in the U.S. CUP cards have been accepted in the US since December 2005, and Discover Cards have been accepted in China since November 8, 2006.[4] This partnership makes Discover Card the most widely accepted American card in China, beating out competitors Visa, MasterCard, and American Express. Neither Discover Financial Services nor China UnionPay have stated whether there had any plans to eventually expand acceptance to the other nations where the CUP network is in place, i.e., the Philippines, Singapore, Thailand, Vietnam, and South Korea. A similar agreement was made in August 2006, when the Discover Network announced an alliance with Japan’s JCB Network.[5] JCB Cards will be accepted on the Discover Network in the United States, Puerto Rico, Guam and Northern Mariana Islands starting October 12, 2007 and China UnionPay Cards will be accepted on the Discover Network in the United States, Canada, Mexico, Central America and the Caribbean starting November 1, 2007[6].
On August 24, 2006, Discover’s PULSE network and the UK’s LINK ATM network announced a reciprocal agreement that will allow the more than 4,500 financial institution participants in the PULSE network to offer their cardholders access to all but a handful of the more than 58,000 cash machines across the UK and allow LINK to offer its 38 participating financial institution members access to more than 265,000 PULSE cash machines in the United States.[7]

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So it looks like acceptance in Europe is minimal. Discover Cards can be used at ATMs in Europe, but places that cater to tourists seem to be the only places that accept Discover. The same is true for Canada. I hope this excerpt helps.

I know in America, most places seem to accept at least Visa/MC, most accept Amex and some Discover. What about outside of the US? Discover is pretty much non-existent elsewhere. I seem to recall that some Canadian shops usually accept either Visa or MC but not both. At the very least, a Canadian financial institution doesn't issue both (I think this changed recently).

I'm just wondering if its worth getting different cards using the three major networks that have 0% forex fees in case I travel or make a purchase from a non-US web site. I am planning for an small AOR (4 cards tops) and I am thinking about the Schwab Invest First Visa, a Cap 1 cashback MC, or any AmEx card that has no fee.