Destinations available online from Prague include:

Berlin
Dresden
Hamburg
Stralsund
Munich
Nuernberg
Frankfurt
Erfurt
Leipzig

https://www.cd.cz/eshop/international/info.aspx

Prices range from 19 euros to 49 euros, and tickets are valid only on specific trains, on specific days. At least three-day advance purchase is required, but you cannot purchase them more than 60-days out.

Of course, these tickets also cover the intermediate cities (so you can buy a ticket to Erfurt but get off at Weimar).

Just looking at some sample dates next week, the tickets were cheaper on the Czech site than the discounted fares on DB.