Two are Ampelamus albidus AKA Cynanchum leave (honeyvine, sandvine) and Matelea obliqua (climbing milkvine).

I would not call these "unusual" monarch hosts. They are native to the US. People who have the honeyvine in Ohio find it to be popular with mama monarchs late in the season.

If you can untangle this FAQ that became serialized after the Houzz transition, there are a fair number of non-asclepias in the list.

http://faq.gardenweb.com/discussions/2765898/monarch-hostplants-includes-all-milkweed-and-common-names

Apocynaceae (Dogbane)
Apocynum androsaemifolium Cosmopolitan ([creeping, flytrap, spreading]dogbane; Indian hemp, bitter root)

Asclepiadaceae (Milkweed)
Araujia sericifera Nearctic (white bladderflower, cruel vine, cruel plant, bladder vine)

Asclepias amplexicaulis USA ([blunt-leaved, bluntleaf, sand, clasping]milkweed)
A. asperula USA (antelope-horns, [green-flowered, antelope horn, spider]milkweed)
A. californica USA ([California, Sierra]milkweed)
A. cancellata Nearctic (wild cotton) A. cordifolia USA ([purple, heartleaf]milkweed)
A. curassavica USA {syn: A. nivea, A. bicolor} ([annual, scarlet, tropical, Caribbean]milkweed; bloodflower, butterfly-weed, silkweed,
cotton bush, pleurisy root, red top, redhead, sunset flower, cancerillo, ipecacuanha,
koningsbloem, Indian root)
A. curtissii USA ([Curtiss's, sandhill, scrub]milkweed)
A. eriocarpa USA ([Monarch, Indian, butterfly, woollypod, woolly]milkweed)
A. erosa USA (desert milkweed) A. exaltata USA {syn: A. phytolaccoides} ([poke, poke-leaved, tall]milkweed)
A. fascicularis USA {syn: A. mexicana} ([narrowleaf, narrow-leaved, Mexican whorled, Mexican]milkweed)
A. hirtella USA ([tall green, prairie, green, Barrens]milkweed)
A. humistrata USA ([sandhill, pinewoods, purple, scarlet]milkweed)
A. incarnata USA ([swamp, rose]milkweed)
A. lanceolata USA ([red, fewflower, smooth orange, pineland, lanceleaf, lanceolate, few-flowered]milkweed;
purple silkweed)
A. latifolia TX (broad-leaf milkweed) A. longifolia USA ([longleaf, Florida]milkweed)
A. obovata USA ([pineland, green]milkweed) A. oenotheroides USA ([zizotes, Texas, longhorn]milkweed)
A. perennis FL ([white swamp, aquatic]milkweed)
A. physocarpa Cosmopolitan (goose plant, balloon plant, balloon cotton bush, balloon cotton, swan plant, pod milkweed)
A. purpurascens USA (purple milkweed)
A. rubra USA (red milkweed) A. speciosa USA (showy milkweed)
A. subulata Cosmopolitan ([desert, rush]milkweed; candelilla)
A. subverticillata Cosmopolitan {syn: A. galioides} ([Western whorled, horsetail, poison, bedstraw]milkweed; Navajo Name: Ch'il'abe's'óóz)
A. sullivantii USA ([prairie, Sullivant's, smooth]milkweed)
A. syriaca USA {syn: A. cornuti}(common milkweed, silkweed, wild cotton flower, wild cotton)
A. tomentosa USA ([velvetleaf, hairy, tuba, sandhills, velvet]milkweed)
A. tuberosa USA (butterfly[weed, plant, bush];[pleurisy, wind, white, Canada, orange, tuber, flux]root;
chigger[plant, flower];[butterfly, Rolf's, orange, yellow]milkweed;
Indian paintbrush, Indian-posy, swallowwart, orange swallowwort, Southern butterfly weed)
A. variegata USA ([white, redring, green-flowered, variegated]milkweed)
A. verticillata USA ([whorled-leaf, whorled, linear-leaved, whorled white, eastern whorled]milkweed)
A. vestita USA ([woolly, Parish's woolly]milkweed)
A. viridiflora USA {syn: A. obovata}([green comet, green, short green, green-flowered, wand]milkweed)
A. viridis USA ([green, oblong-leaved, spider, green antelopehorn, green-flowered, antelope horn]milkweed)

Calotropis gigantea Cosmopolitan (giant milkweed)
C. procera Nearctic (calotropis, rubber bush, apple of Sodom, mudar, madar, king's crown, roostertree)

Cynanchum angustifolium USA (Gulf Coast swallowwart, milkweed vine)
C. laeve Nearctic {syn: Gonolobus laevis, C. sinaloense, Ampelamus albidus} ([sand, blue, honey]vine; [honeyvine, climbing]milkweed; angle pod, vine milkweed)

Gomphocarpus fruticosusp Nearctic {syn: Asclepias fruticosa, A. arborescens, G. fruticosus} (narrow leaf cotton bush, Irish ballon, swan plant, balloon-cotton, Cape-cotton, duck bush,
bristle-fruited silkweed, balloon weed, white swan milkweed)

Marsdenia Spp. Nearctic {example species, descriptions follow} (M. cundurango (Cotton root); M. zimapanica(Mex), large climbers, latex sap)

Matelea reticulata USA ([pearl, net-vein, netted]milkvine; milkvine, pearl milkweed, green milkweed vine)

Morrenia odorata FL ([strangler, milkweed]vine; tasi, Florida milkweed vine, latex plant)

Sarcostemma clausum USA (white twinevine, white milkweed vine, viney milkweed, whitevine, narrow-leaf milkweed vine)
S. crispum TX (wavy-leaf milkweed vine, wavyleaf twinevine, wavyleaf climbing milkweed, wavyleaf milkvine)

Convolvulaceae (morning glory)
Ipomoea Spp. Nearctic

Malvaceae (Mallow)
Gossypium arboreum Nearctic {available in TX}(cotton tree, tree cotton, devkapas)

Rutaceae (Citrus)
Citrus Spp. Nearctic

Sapotaceae (Sapodilla)
Manilkara grandiflora Nearctic ( ? possibly M. zapota)

I'mggoing to test that citrus and sapodilla thing

Where did this list originate? I'd like to verify this.

Thanks,

Jane

Looks like the FAQ copied and pasted into a comment, this restored the proper newlines, makes it readable. I compiled the list over 10 years ago by compiling google search results for monarch+hostplants, and then searching for common names of each resulting hostplant.

If you want to wade through the 126 results from the HOSTS database and pick out the USA, hawaii, and nearctic results, here it is:

http://www.nhm.ac.uk/our-science/data/hostplants/search/list.dsml?searchPageURL=index.dsml&Familyqtype=starts+with&Family=&PFamilyqtype=starts+with&PFamily=&Genusqtype=starts+with&Genus=dan&PGenusqtype=starts+with&PGenus=&Speciesqtype=starts+with&Species=plexi&PSpeciesqtype=starts+with&PSpecies=&Country=&sort=Family

Thanks logician. I did check a couple of them and they seemed real though in other continents.