The following are intended to be used to make more varied varieties of monstrous spiders. These are fairly simple and each one only modifies a few traits. As such they will not be in full template format. Some may have CR modifications, but take them with a grain of salt; for example a bell diver doesn't have a listed CR increase but unless the party has reach and is prepared for underwater combat it is significantly more threatening at high sizes than a regular monstrous spider, though I do not think it is in and of itself enough stronger to justify a CR increase (water encounters are generally harder unless a party is prepared, monstrous spiders size up poorly against equal CR elementals at higher CRs).
Asphodel: Native to the Gray Waste, Asphodel spiders can be either web-spinners or hunting spiders. They gain a +4 racial bonus on saves versus poison, and their poison deals Int, Wis, and Cha damage instead of Strength damage. Their CR is approximately the same as few characters use all three, but it does make them less potent against low level melee, more potent against casters, and more likely to take out a character in a single bite at high levels which may justify a CR increase on Colossal spiders.
Bell-Diver: A bell-diver spider is a variety of spider which hunts by diving underwater in an air bubble which it creates. They are neither web-spinners or hunting spiders, but use the latter's skill bonuses (+10 to jump, +4 to hide, +8 to spot, +8 to climb, may use Dex instead of Strength) except they also gain a +8 racial bonus on any Swim check to perform some special action or avoid a hazard, can always choose to take 10 on a Swim check, even if distracted or endangered, can use the run action while swimming provided it swims in a straight line, and can use Dex instead of Str on Swim checks. A bell-diver spider has a swim speed equal to its climb speed, and surrounds itself with an air bubble (this is an Ex special quality). This air bubble extends out from the spider up to 1/2 their natural reach and the spider can swim despite this (by reaching outside of the bubble). A creature smaller than the bubble may find itself stuck floating at the surface of the bubble unless they can stand on water or fly.
Cannibalistic: A cannibalistic spider is a variety of spider which hunts other spiders. They may be web-spinners or hunting spiders. Cannibalistic spiders may move freely through the webs of other spiders, gain a +4 to checks and saves against webs (including the web spell), and a +4 racial bonus to saves versus poison which increases to +8 against spider poison.
Funnel-Web: Australian funnel-web spiders possess some of the deadliest spider venom on Earth. The monstrous variety is no different. Web-spinning spiders, funnel-web spiders have a +3 racial bonus to their poison save DCs, their poison deals damage as shown on the table below. Their CR is increased by 1; they are potentially more deadly even than that but their lower save DC, worse to hit, and significantly worse hp compared to a monstrous scorpion makes up for the doubled poison damage
Size Poison Damage Tiny 1d4 Con (DC 13) Small 1d6 Con (DC 14) Medium 1d8 Con (DC 15) Large 1d10 Con (DC 16) Huge 2d6 Con (DC 19) Gargantuan 2d8 Con (DC 23) Colossal 3d6 Con (DC 31)
Widow: The various 'widows', black, brown, and red, are some of the most infamous spiders. Web-spinning spiders their neurotoxins inflict nerve damage. They have a +2 racial bonus to their poison save DCs and deal damage as shown on the table below. Their CR is increased by 1, though they are weaker than funnel spiders and noticeably weaker than scorpions and at the higher CRs may not be worth the increase (despite their poison being noticeably more deadly than a centipede's). As an option a creature that rolls a nat 1 on their save versus monstrous widow poison takes drain instead of damage; this helps make up the CR difference, but should not be used at low (1-3) levels, or in campaigns where magical healing is especially hard to come by.
Size Poison Damage Tiny 1d4 Dex (DC 12) Small 1d6 Dex (DC 13) Medium 1d8 Dex (DC 14) Large 1d10 Dex (DC 15) Huge 2d6 Dex (DC 18) Gargantuan 2d8 Dex (DC 22) Colossal 3d6 Dex (DC 30)