Luggage and bags:
Rocky Mountain National Park offers great backcountry camping so a backpack is something you should bring even if you have just been thinking of giving it a try. A day pack is essential to carry extra clothing and food on day hikes into the mountains.
Clothing/Shoes/Weather Gear: A good pair of sturdy hiking books with ankle support is what you need for tackling the many trails of this hiking paradise. Warm cushioned socks will make your feet happy. Synthetic layers are best for this high elevation park. Bring a warm hat! While it is in sunny Colorado, much of it is over 8000 feet and weather is changeable any time of year. Rain gear is another thing not to forget. Thunderstorms are common in summer and drizzle anytime the sun is not out.
Photo Equipment: A wide angle lens allows you to bring things into the foreground of your photos, making them more interesting. A zoom is needed for wildlife photography. You don't want to get too close to a rutting elk! A tripod is great for low light situations and cute couple shots.
Camping/Beach/Outdoor Gear: Rocky Mountain National Park is a camping paradise. Bring your tent, a warm sleeping bag, sleeping mats and a camp stove. You'll save money and see more of the nature you came for in the first place.
Miscellaneous: D proves that even when the opportunity is not there, by improvising and going with the flow, you can make Plan B every bit as good as Plan A.
Sturdy hiking shoes, multiple layers including rain jacket and long sleeves (preferably wind-resistant), a hat and sunglasses
Toiletries and Medical Supplies: Sunscreen or aloe for burns might be handy during the summer. The elevation leaves more room for problems without appropriate precautions. Mosquitoes are a slight problem at certain lakes and ponds, so repellent may come in handy.
Photo Equipment: zoom lens if possible
During three days in July at Rocky Mountain National Park we saw warm sunny skies, dark clouds, rain, and in the higher elevations, snow and sleet. Come to think of it, we saw all of those conditions in just one day. Be prepared for anything.
Remember that mountains like these create their own weather, so it may be quite different here than in the cities nearby from which you hear a weather forecast. Just 30 minutes before taking this picture of Hidden Valley, from Rainbow Curve along the Trail Ridge Road, the sky had been clear and blue. Shortly after this photo the rain came in torrents, and that evening the stars sparkled above our campsite in a black velvet sky. That day we had worn shorts and T-shirts. In the evening tempertures dropped to around 40F.
Photo Equipment: In Rocky Mountain National Park you'll be ooohing and aaahing at every turn. Bring twice as much film or digital capacity as you think you'll need. Chances are you will also see plenty of wildlife, so bring a telephoto lens or any other appropriate equipment you have.
Camping/Beach/Outdoor Gear: Be prepared for cool evenings, even during mid-summer.
Luggage and bags:
If you come to this park you won't need much luggage because you won't need to dress up. Restaurants are all casual.
Clothing/Shoes/Weather Gear: Bring a wind breaker for cool nights and rainy days (summer).
Other months than June, July and August...you might need a jacket, gloves, etc. The weather can be cold and snowy.
Lightning storms are common, don't get near old dead trees, they are good conductors.
Toiletries and Medical Supplies: There are stores in Estes Park in case you need this type of thing and forgot it from home.
Photo Equipment: You get so close to the animals that your friends will think you are an expert at photo making.
Camping/Beach/Outdoor Gear: If you plan to back pack in the park, you must get permission and receive a permit.
Always ask about bears, and put your food on a rope from a tree. Do not leave food in your car overnight if you are camping.
Miscellaneous: It is stupid to feed large animals, this can be dangerous.
The park also has a rule not to feed animals which includes the chipmunks, pikas, birds, etc.
All fish caught, must be replaced back into the water.
Camping/Beach/Outdoor Gear: If you're hiking for more than 5 miles altogether, or you're expecting to spend the night in a backcountry campground, you'll probably not be able to hike in enough water to prevent dehydration. (If you did, your backpack would have room for little else, and its weight would be enormous). Better to carry a small receptacle and a good water filter. Very few places in Rocky are without a running stream of some kind, so there is generally a sufficient water source in the areas where you are heading.
Camping/Beach/Outdoor Gear: Rocky is an outdoorsman's paradise. Backcountry camping is allowed is a large handful of alpine sites, many of them at 10,000 ft or higher. For such expeditions it's always useful to have a good backpack to carry your things, and a small, easily-packable tent and a lightweight but thermal rated sleeping bag -- overnights in Rocky, even in the summer, can drop below 40 F.
Smart people - like my brother and sister-in-law - bring rain gear, warm sweaters, and good footwear even for a short stroll in Rocky Mountain National Park.
Not so bright people like Yooperprof are caught unprepared when it starts to hail at 12,000 feet. Oh well.