The "ham call signs" you're hearing below 28000 aren't actually ham callsigns. They're 11 meter DX callsigns (the first character(s) should always be a number). Check out this list of 11-meter "callsign" prefixes
http://dxprefixes.blogspot.com/. These stations are all freebanders, but there's quite a lot of order to it considering its all illegal DXing below 28000.
Glad to see the band is opening up again. 27025 is CB channel 6, used by operators running at least several kW.
99.99% of stations will be on frequencies ending on either 0 or 5 since most operators are using channelized radios. The UK FM CB allocation is 27601.25 to 27991.25 in 10 kHz steps, so if you're hearing something in FM with a weird offset, chances are its UK based (or somebody using a radio set for the UK channels).
Here's some quick logs starting at 1650 UTC
25000 AM - WWV loud and clear
25875 AM - Spanish language taxi dispatch
25950 FM - STL (weak)
26225 USB - Spanish language, strong signals
26305 AM - Truckers
26475 AM - Spanish language, heavy fading, possibly taxis
26495 AM - Spanish language, similar to 26475 AM
26555 LSB - Spanish language, very strong signals
26585 AM - Spanish language, heavy QRM
26655 AM - Spanish language, Mexican accents, OTH Radar QRM
26715 AM - Puerto Rico (very loud signals)
26805 AM - Spanish language activity - likey taxi dispatch
26835 AM - "Mister 155 Puerto Rico" very strong signals
26965 - 27405 - legal 40 channel US/European CB band
27415 LSB - US stations, Kentucky heard
27425 LSB - "you take care and have a good one now"
27425 AM - Spanish language taxi dispatch
27435 LSB - "73s 522, this is 001" "yeah 35 Indiana, how are you, over?"
27455 USB - Spanish language
27480 USB - Spanish language
27485 USB - Spanish language, S9+ signals
27515 AM - Spanish language taxi dispatch
27555 USB - International 11-meter calling frequency - 26 India Sierra 002 Scotland calling CQ DX (lots of other stations on frequency)
27625 USB - French language
27700 USB - SSTV (weak)
27715 USB - Spanish language
27781 FM - UK FM channel 19, heavy fading
27785 USB - Spanish language