Loco2?

It's a new booking agency for European rail fares that tries to be a one-stop shop without the complications (and, for Americans, sometimes money-gouging tactics) of individual national rail sites. I haven't used it yet but the Seat61 site endorses it and that's good enough for me.

For trains in Germany, use the German Rail website. I would be concerned about Loco2 because their schedule does not agree with that of German Rail, who should know their own schedules. Other than that, the fares they show seem to be the same as those on the German Rail website.

However, compared to RailEurope, they do show discounted fares.

Added: I also noted that this website does not understand Länder-Tickets. For routes like Munich to Salzburg or Munich to Fuessen, it shows the regional trains with full fares, not Bayern-Ticket prices. But then, neither does RailEurope. This is a much better site than RailEurope. It is definitely a good place to get fares to compare to a rail pass since it seems to cover all countries.

I spent many hours looking at the different train sites to book tickets for 3 countries which all have different ways to use their site. I found this site throughout man in seat 61 and just used it a few days ago to book 5 train trips in 2 countries. The trains I need to spain are not available for booking yet and the site let me set up a reminder for them to contact me when it became available. So far, I love this site and will use it in the future as it is so much easier to book with for a U.S. person.

Looks like an interesting site. Note, however, that by their own admission, they do not offer many of the discount fares available on the native sites for Italy, Spain, others: "However we are not able to offer the full spectrum of cheap advance fares and so you can often find cheaper prices booking directly at TrenItalia.com."