If you have either an Apple or Android phone, and an Apple TV or a Chromecast, you can Airplay or Cast the screen to the TV.
Basically if you've got an iPhone or iPad you need an ATV3 (I have a brand new one here I can let go for cheaps if you want it), or if you have an Samsung or other billionty phone or tablet you need to buy a £30 Chromecast device. Both plug straight into your HDMI TV, and let you stream stuff.
They're awesome. Or you can plug your laptop into your TV via HDMI (if you have an HDMI out port on it), but you won't get the sound from anywhere other than the laptop.