Freeform radio lives on on the lower frequencies and online.
It may be found on random pirate or college or community-supported stations.
Not every locale has such treasures, sadly.
But thankfully some of the better examples of freeform radio may be heard online. Just google the station you're looking for and hope that their technology budget is generous enough to allow archival streaming.
The following stations are likely to broadcast freeform, at least in part: WPRB, KFJC, WCBN, WMNF, KUMM, WPNK, WAMH, KEXP, WFMU, KDRT, KDVS and WNYU.
My favorite is on WMBR, the station for MIT.
MIT has a few different shows that qualify as being "freeform radio" but the best, hands down, is done every Wednesday at four PM EST and lasts about 90 minutes—it's called In the Margin. What makes this one special is that the whole set is mixed and mostly seamless with only the occassional, obligatory interruptions for PSAs and station ID. Often (but not always) the show will have a (sometimes topical, sometimes specific) theme which each track touches on, marginally. In the Margin has two non-student DJs who alternate weeks on the decks. They've been doing this thing for years and make it sound easier than it is.
Oh yeah, and you can stream their two most recent shows on the station's website, so you can listen anywhere.
Remember that stations that eschew radio blandness are more likely to rely on listener contributions, so consider donating if you like what you hear.
& if you wish to find stations by location or content, check out this radio locator. In case you were curious, call letters for radio stations are ordered loosely:
the letters K and W originated early in the 20th century as part of a worldwide index of ship radio stations. K stood for ships on the East coast of the US, W for ships in the Pacific. For some reason, when the letters were extended to land-based stations, they were reversed, with the Mississippi River eventually adopted as the dividing line. Ever since 1923, stations west of the river start with a K, those east of it start with a W.
/straightdope of course there are some exceptions to the above, notably in Pittsburgh. And plus this arbitrary line was originally just west of the Mississippi River too... For a more detailed explanation, check out A Brief History of Radio.
And yes, the above call letter info is very specific to the US with respect to listening on the AM/FM band. To find your non-US country's call letters, go here.