What are some good, personalisable online radio / music apps?

There's a lot of them out there, but they all have their assorted quirks, making different ones better for different things.

For example, last.fm doesn't allow pausing, Pandora is US-only, and so on.

It'd be great if people could post one service per answer, and use a format to allow easy reading and comparison, such as:

Name (www.website.net)

Short description/tagline/similar, (keep it brief, use Extra Details section for more).

Restrictions

• only plays X music
• country/region restrictions
• limited to X browser/client
• etc

Pros

• benefits to this service
• which the average doesn't have

Cons

• missing or bad features
• not covered by restrictions
• e.g. no pausing

Extra Details

Any other rambling stuff you want to write to add detail not provided by the above sections

From web app Peter Boughton

• I used to listen to last.fm but it became so repetitive, now when programming I put on http://radiotuna.com, click "Chilled", "Trip Hop" and the stations there are perfect for relaxed concentrating over a long period of time.

  From Edward Tanguay

• A good alternative I can recommend is "The Sixty One".

  While it's probably not directly as you described, it's a brilliant way of finding new and (most likely) unknown music, the flow is great, and it has quite a bit different styles. On top of that, it has a funky optional quest-system, that gives it a rather unique touch.

  To summarize, I'd add it as this, hope that helps:

  The Sixty One (http://www.thesixtyone.com)

  Pros:

  • Nice way to find new music
  • Great radio-system
  • Lets you save music, and have different playlists
  • Option to donate money to some of the artists, and upvote songs.
  • Some tracks are available as free/paid downloads
  • Fun and different quest- and achievement-system

  Cons:

  • A bit tricky UI, that takes a while to get used to (an older version is still running here: http://old.thesixtyone.com/ It might be easier to get around)
  • Has some various bugs from time to time
  Justin L. : I do personally recommend the older version, because you can browse lists and charts without stopping the song you are currently listening to.
  From Gnub

• Grooveshark (www.grooveshark.com)

  Online Music streaming, music recommendation and sharing

  
  Restrictions

  • It is flash based (if that is a restriction)
  • Mobile apps are available only for paying customers.

  
  Pros

  • Great UI
  • Large collection of songs, ability to create, save and share playlists
  • A good song recommendation engine
  • Radio
  • Internationally available
  • Free

  
  Cons

  • Non-paying customers can't use mobile apps
  From Krosmos

• Pandora (www.pandora.com)

  Pandora uses the Music Genome Project to find and play music you might like based on artists and pieces you tell it you already enjoy. You can then vote up or vote down individual songs, and it will learn what types of music you like and give you additional music that suits your tastes.

  
  Restrictions

  • You cannot choose to play an individual specific song
  • Only available in the USA
  • You cannot skip ahead or back within a song, but can skip a song entirely
    • Limited to 6 skips per hour per station, 12 skips total per day
  • Limited to 40 hours per month, costs $0.99 to continue using for the rest of the month if you go over the limit

  
  Pros

  • Exposes you to tons of new music which you'll probably enjoy and might not have known about
  • Has free Windows 7/Vista desktop gadget, iPhone/iPod app, and an easy-to-use web interface
  • Is pretty smart about learning what you like
  • Multiple "stations", so that your interests in music can be kept separate. Things you "like" in one station won't affect what you get in another station, providing some separation if you have diverse music tastes but don't want genres to overlap.

  
  Cons

  • Restrictions (see above)
  • Doesn't have as much music by independent artists, but there is some

  
  Extra Details

  I highly recommend Pandora. I use it very frequently, and it's a nice way to listen to music you already like and hear new music.

  The lovely desktop gadget:

  

  Lipis : Too bad is working only in USA..!!
  From nhinkle

• Musicovery
  Play your mood

  Restrictions
  flash based, a notch slower to load than the other similar websites, an okayish UI

  Pros
  good streaming, excellent song recommendations, can post directly to social websites

  Cons
  none as such

  Extra Details
  A screenshot!

  

  serg555 : Well, if you decide to use it for free then there is quite a few cons you didn't mention, like very low quality and inability to control playback.
  From Lazer

• Jango

  Subscribe to specific artists, like/dislike songs and get recommendations for more songs, Just Works TM.

  Pros - Free - No funny features like 'props' or DJ capabilities , just plain old internet radio that works. - Easy setup - select a bunch of artists you like, and train the recommendation engine by liking/dislking songs.

  Cons

  • Not all music is available at all time. You can search for specific songs, but at times some songs might not be available for playing (due to licensing issues I think).

  

  From ripper234