The Man in Seat 61...
Like me, Jamie and Kate use the trains themselves for their journeys around Europe, and thought there ought to be a far better way to book them, all in one place. So they put their money where their mouths were and started www.loco2.com from scratch. Their ethos is to connect to as many of the individual national rail booking systems as possible to sell the same tickets as the operators themselves, at the same prices with no booking fees, as simply as possible.
You can use www.loco2.com wherever you live, as they accept all international credit cards and ticket delivery is usually print-at-home or collect-at-station.
So far, here's a list of the system to which they've connected Loco2.com:
British national rail: Loco2.com can sell most UK train tickets with no booking fee & collect-at-station delivery, including SailRail tickets to and from Ireland. This also means that they can sell tickets to mainland Europe starting at any British station - the only site to date with such a capability. And they also sell the special tickets from British stations to London International CIV for use in conjunction with Eurostar, one of the few sites to sell these separately online, as explained here.
SNCF French Railways: Loco2.com connects through uk.voyages-sncf.com's datafeed to sell French train tickets and Eurostar, in pounds at French Railways own prices with French Railways & Eurostar's own print-at-home or collect-at-station delivery. They'll also send tickets to UK addresses. Note that connection via uk.voyages-sncf means they can't currently sell tickets for the special iDTGV trains, or a handful of special products such as espace privatif (sole or dual occupancy or a 4-berth couchette on a night train) or forfait bambin (a flat fare to give infants their own seat), to book these I recommend a similar site started by three young French entrepreneurs for similar reasons, www.trainline.eu.
DB German Railways: Loco2.com connects to the same system that drives DB's own site bahn.de, to sell train tickets to, from and within Germany, as DB's own prices with DB's own print-at-home tickets and no booking fees. Payment for DB bookings made on Loco2 is taken in euros, via DB's own payment system. Note that the datafeed provided by DB can't do sleeper trains, but many of these overnight services can be sold though Loco2's connection to uk.voyages-sncf.
Renfe Spanish Railways: Loco2.com connects to Renfe to sell all Renfe's cheap tickets with Renfe's print-at-home ticket delivery. Payment is taken in pounds. The system can also sell the international sleeper trains from Madrid and the French border to Lisbon in Portugal. Given that Renfe's own site has a reputation for quirky translations and rejecting a significant proportion of overseas credit cards, Loco2 becomes a great way to book Spanish tickets with no fuss, even if your own bank account is in euros or dollars.
Italo: Loco2.com also connect directly to Italo, the privately-owned high-speed operator in Italy competing with State-owned Trenitalia on the Milan-Florence-Rome-Naples & Venice-Florence-Rome routes.
Trenitalia Italian Railways: As of March 2015, Loco2.com also connects to Trenitalia, to sell Italian train tickets at the same price as Trenitalia, with payment in pounds, and either collect-at-station tickets or for fast trains, it's ticketless - you just quote the booking reference on board the train.
Using these systems, they can sell through journeys that involve multiple operators. For example, Paris to Seville, sourcing the Paris-Barcelona TGV from the French system and Barcelona-Seville train from the Spanish system. Or Paris to Venice, sourcing Paris-Turin from the French system and Turin-Venice from the Italians, ensuring you get the cheapest price for each leg and the operator's own print-at-home ticketing.
Do I recommend Loco2 for every European train route? No, because they're not yet connected to the Austrian, Swiss, Polish, Czech or Hungarian systems, for example. But they're working on it!
Booking tip: The 'More options' feature is worth remembering, to specify a 'via' station or enter a stopover. Use it with zero duration specified if you want a particular route, for example London to Nice via Lille rather than Paris. Specify a duration if you want a stopover, for example London to Barcelona with time in Paris for lunch. In most cases, the effect of specifying a stopover is to split the ticket at that point - sometimes if the system struggles to find an option, specify an obvious routing point and it finds a journey! Or if you want to see if Paris-Barcelona is cheaper with a split-ticket at Perpignan, simply enter Perpignan as a stopover.