Actually, there is really no such thing as an espresso coffee bean per se. "Espresso" refers to the method of making the coffee, not to the bean itself. However, many coffee roasters market particular roasts as "espresso roast", using beans that have qualities that are conducive to the production of crema. Many think of an espresso roast as being dark, but this is also not necessarily the case. The main thing to look for in a roast that is going to be used for making coffee using the "espresso method" is that it generates good crema. Other than that, you need to find a blend that appeals to your personal taste, be it a light, medium, or dark roast.
How I Improved My Espresso Coffee and Saved Money by Buying Quality Espresso Beans Online
I personally prefer to buy my espresso coffee beans online not only for convenience and price, but also because it gives me access to specialty bean roasters. Over the years I have purchased online from various sources, including Green Mountain Coffee Roasters, Peet's Coffee, Sovrana Store, and more recently Cafe Maison and Espresso Vivace Roasteria. I have found them all to be reliable. Of course, Sovrana, Cafe Maison, and Vivace are much smaller than GMCR and Peet's, but they lack nothing when it comes to service and quality. Sovrana always had my order on my front porch within 2 days, but I guess they have an advantage in that they are located close to where I live. They actually are not coffee roasters, but resellers of the Italian brand known as "Lavazza".
Cafe Maison provides more of a personal touch. They roast their own beans, and your order comes with a label attached to the bag that says "Roasted for..." with your name inserted. The packaging is plain clear plastic (at least in the case of the 5lb bags I always have in my order), but who cares when their roasts are superb in my point of view. Each of their 3 espresso roasts make great crema. At the time of writing, if your order is over $75 and you live in the lower 48 United States, you qualify for free UPS ground shipping. I always take this option as my typical order is for 10lb of coffee which just tips the $75 scale. If you do take this option, though, bear in mind that it may take up to a week for your coffee to arrive, so plan ahead; you don't want to run out, right!
Another great roaster I happened upon recently is Espresso Vivace Roasteria based in Seattle. While visiting Seattle recently, I was given a bag of their Vita espresso roast, and it was exquisite in flavor and crema production. I just ordered 3lb of beans from them, including the Vita roast and their other espresso roast called "dolce". I must say that both are good, but that my personal preference is for "vita".
Of course there are many other options available out there. Illy always gets rave reviews, but I personally think you have to pay too much for the brand in that case. Cafe Maison actually advertises as making roasts that taste just like Illy's. Right now for my favorite online coffee bean retailer, it's a toss up between Cafe Maison and Espresso Vivace Roasteria. Both roast excellent espresso beans and offer great service and reasonable pricing.
For years I always hoped that I would be able to find some great beans at Amazon. I tried a few, some were really bad, such as "Eight O'Clock" coffee beans. Copper Moon Guatemalan Antigua Blend are pretty decent and I have recommended them, but I always hoped for some Ethiopian Yirgacheffe beans as these are my favorite varietal for espresso, but for a long time there were none available at Amazon until I finally found these Coffee Masters Gourmet Coffee, Ethiopian Yirgacheffe in early 2013. As of this update in November 2015, I still have these on monthly order through Amazon's Subscribe and Save program. Take that as my seal of approval as I have never stuck with a line of beans this long before.
Please note that I have absolutely no affiliation with Cafe Maison nor Espresso Vivace other than as a satisfied customer of both. I am however a member of the Amazon Affiliate program. But everything I recommend from Amazon is only after I have made my own purchase of the product. As I mentioned about, I continue to purchase the Coffee Masters Gourmet Coffee, Ethiopian Yirgacheffe on a monthly basis because I find they meet my taste preferences and always allow me to make espresso coffee with perfect crema without fail.
For years I always hoped that I would be able to find some great beans at Amazon. I tried a few, some were really bad, such as "Eight O'Clock" coffee beans. Copper Moon Guatemalan Antigua Blend are pretty decent and I have recommended them, but I always hoped for some Ethiopian Yirgacheffe beans as these are my favorite varietal for espresso, but for a long time there were none available at Amazon until I finally found these Coffee Masters Gourmet Coffee, Ethiopian Yirgacheffe in early 2013. As of this update in November 2015, I still have these on monthly order through Amazon's Subscribe and Save program. Take that as my seal of approval as I have never stuck with a line of beans this long before.
Please note that I have absolutely no affiliation with Cafe Maison nor Espresso Vivace other than as a satisfied customer of both. I am however a member of the Amazon Affiliate program. But everything I recommend from Amazon is only after I have made my own purchase of the product. As I mentioned about, I continue to purchase the Coffee Masters Gourmet Coffee, Ethiopian Yirgacheffe on a monthly basis because I find they meet my taste preferences and always allow me to make espresso coffee with perfect crema without fail.
Please see this post for details of my recommendation for Copper Moon Guatemalan Antigua Blend that I mentioned above. Depending on personal taste, you may prefer these beans: Great Value Coffee Beans Suitable for Espresso.