Unfortunately, the MashUp Addon has been discontinued. I personally used this a bunch and it is sad to see it go. There are however still many good alternatives.
1) 1Channel – Although not always in HD 1Channel is full of content and is unmatched in quantity.
2) Icefilms – Another oldie but a goodie. This addon usually only has recent shows, however, you can almost always find it in HD.
3) Genesis – A new one that shows streams from a bunch of sources just like mashup. I recommend this if you liked having options to stream from without having to go into each addon separately. CLICK HERE FOR INSTALL INSTRUCTIONS
4) SportsDevil – Sports devil is still one of the best addons for sports.