UUUUGGGGHHHH!!!!
We rent houses w/dh's extended family in Cape Cod every year. I ALWAYS bring my own linens just because.
I bring:
1 Flat Sheet per bed
1 Fitted sheet per bed (see tip)
Pillows
Pillowcases
Mattress Pad (for at least my side...I'm like the Princess & the Pea!!!

)
One tip: When bringing your own linens, bring a fitted sheet. You can just slip this right over the existing linens (if there are any) and pillows (I'm a nut...don't judge me!!!!

). This way, when you leave all you have to do is collect your linens and the bed are already made!!!!!
I also bring:
Bathroom rugs
Assorted Cleaners (bathroom & toilet)
Hand soaps (pump kind is easier w/Kids)
A caddy for shampoo's & shower necessities since the kids like to shower outside and we are "sharing" the house w/one other family group.
Towels
Wash cloths
hand towels
beach towels
kitchen towels (cheaper & takes up less space than all those paper ones!)
We have pared our kitchen supplies down to:
DH's favorite frying pan
My teapot
Coffee/tea mugs
flat spatula
Then the FOOD!!!!!!!!!! I shop at our discount grocery store for most of the food ahead of time becaus I HATE going grocery shopping on my vacation.
Add all this stuff to the boogie boards, sand pails, boat, bikes,
scooter, and I'm not sure where my 13 year old niece is going to sit!!!!!!!

Not to mention her "stuff" too.
I never have looked at renting a cottage/house as a vacation...it is just the same thing as being at home only with sand and salty water thrown in to make eveything pleasant!!!!

I still like to go though...
