The delta loop would be a good start, especially if you can get it high enough in
the trees. Best configuration would be with the point down and the top wire strung
between two supports, fed in the bottom corner. If you only have one support then
a diamond or a delta with the point up are reasonable alternatives. Feed it in the
bottom center in any case (unless it is very low - under 15' perhaps.)
By adjusting the proportions of the loop you can vary the feedpoint impedance to
improve the SWR (assuming you've already adjusted the circumference of the loop
for resonance in your desired portion of the band. By making the loop a tall and narrow
rectangle (about twice as high as it is wide) and feeding in the middle of the bottom
wire you can get a pretty good match to 50 ohms. http://kt4qw.com/acan1.htm
JA1HWO's "Sky Door" is an extension of this principle: http://mk1502.web.fc2.com/antmenu.htm
(If you use Babelfish to translate the Japanese text it may take some creativity to
interpret the result...)
Even a simple wire dipole can work well at 60'.
There are various wire antennas that can provide gain, but they also will have
more directivity, so you need to know what direction to point them in. Here
are some possible options: http://www.i1wqrlinkradio.com/antype/ch17/chiave47.htm
I used a Bisquare years ago on 20m and 10m with good results. It has a high
impedance feedpoint, but a quarter wavelength of 300 ohm twinlead brought
it down to a reasonable value for coax.
Of course you can also build something like a 2-element quad and hoist it
up into the trees, possibly even rotating it manually as desired.
My recommendation is to put pulleys and halyards up to make it easy to
experiment with antennas, then start with something relatively simple and
build up to more elaborate designs as you get more experience and a better
idea of what works best at your location and what directions give you the
most interesting contacts. Aiming for Europe is a good place to start, then
South America and the Caribbean, then Australia, New Zealand, Asia, etc.
Even if you can't rotate the antenna in real time, you can build a directional
antenna that you can lower to the ground, clip the support ropes onto
different points, and raise back up again to move it in steps within a few
minutes, depending where the band is open.