Aegis + Impervious Skin: Status Resistance?

Do these two IOs stack?

Side question: Is there any other status protection/resistance IOs...or are these the only two?

Yes.

To offer some numbers, you can get, at most, 57.5% status resistance from these IOs, by spending six slots. This will reduce the duration of all Holds, Stuns, Immobilizes, Confuses and Fears by roughly 37%, and alongside Health, Sleeps by about 55%.

This means for every 10 seconds you'd normally spend held, you'll spend just over six seconds instead. An improvement, perhaps, but...

This is important:
All characters that can slot this much status resistance, will have at least five powers that enhance resistance - which in turn means that they're stalkers, scrappers, tanks or brutes... each having toggles or clickies in their secondaries that grant protection against the more annoying status effects. All things told, this means the IOs are mostly useless.

Also remember that even if you do manage to stack up 100% status resistance, this doesn't mean the status effect doesn't work - you only halve the duration.

Even at 10000% resistance, you're still subject to about one percent of the original effect.

No single enhancements besides the two you mentioned but there are set bonuses.

To Hit Buff
Adjusted Targeting (6 slots) = 7.5%

Hold
Basilisks Gaze (5 Slots) = 5%

Accurate Defense Debuff
Shield Breaker (3 Slots) = 2.5%

Accurate To Hit Debuff
Cloud Senses (2 Slots) = 2.5%

Pet Recharge
Expedient Reinforcement (2 Slots) = 2.5%

These are the non PVP ones at least.