Here's a starting point that is available for free: the Australian Ionospheric
Propagation Service tools on the web:http://www.ips.gov.au/HF_Systems/7/1
Choose the "Combined HF Prediction" tool.
For point-to-point predictions, click GRAFIX and in a moment a second tab will appear
beside "Choose Tool" with that name. Click it.
It starts on the "Map View" option page. The display defaults to being centered on
180 degrees longitude, which is useful for trans-Pacific paths. (It's a Australian
tool, after all.) Click on "0 degrees" for paths into Europe or Africa from the US.
Then choose the "Circuit" tab. Click on the map to set the location of the transmitter,
then again to set the receiver. You can also enter the Lat and Long into the boxes
if you prefer.
The "Date + T-index" field lets you forecast for a different date (default is today).
It also gives a couple choices for the T-index if you know it from a different source,
otherwise you can choose "Northern Hemisphere" which is probably close enough.
Then hit the "Predict" button a bit further down the page. You get a printed listing
of frequencies and times throughout the day, and you just have to figure out how to
decode it. Find the row for the current hour: the frequency ranges marked with "F"
are the most likely ones to be open; a % sign means it likely will be open (50% to 90%
of the time.) Those with just a dot are worth checking, but will be open less than 50%
of the time.
The second column is titled "OWF": Optimum Working Frequency. This is the recommended
frequency for the most reliable traffic for a commercial circuit. Generally signals will be
strongest on the highest band that is open.
There are other forecast tools on the same page. I use the LAMP tool for local NVIS
coverage, while the Hourly Area Prediction (HAP) will show you color coded plots
for each hour for what bands are open to what areas. These have a button to
select the amateur frequencies, and are convenient for looking at propagation to
areas, such as Europe or South America, where a single point doesn't give a good
representation of the whole area. You have to read the plots carefully and find
the land contours to figure out the areas involved (the plots are a bit small) but
the color coding shows quickly whether 15m is open, for example. And there are
often quirks: the plot I just ran showed that 12m was open to Newfoundland and
southern Ireland, but not to Nova Scotia or England.
Those will at least give you a start without having to buy anything.