I feel at least 90 percent of the parties I have at my own place get about 24 hours or less of planning.
A little while ago, one of my dearest friends had a birthday. I knew it was coming up but was planning to take her to brunch or something. The night before her birthday, her husband messaged me about doing something special.
At the time, neither of us had any idea what we would do. In the next 10 minutes, I decided to have a taco bar party. In all honesty, this was probably the easiest party I have ever thrown.
I chose the taco bar because my friend loves Mexican food, but this idea can easily be adapted if you do not want to have tacos.
Here is what I did for the taco bar: crack dip, easy fiesta beans, soft tacos, hard tacos, tortilla scoop chips, two pounds of ground beef, taco seasoning, two cans of diced tomatoes, one bag of shredded lettuce, one bag of fiesta blend shredded cheese and two cans of Rotel green chilies.
A recipe for crack dip can be found in my “Tailgating with a twist” column, and a recipe for easy fiesta beans can be found in the spectacular semester starters article.
I put all the ingredients in separate bowls and threw the fiesta beans into a bowl instead of loaf dish, so they could serve as a refried bean dip of sorts.
All in all, this whole party cost about $20. The shredded lettuce was the American salad blend from Walmart, $1.49; cheese for about a dollar; tomatoes and chilies roughly 40 cents each; and about $1.50 for 12 soft tacos.
I am not including the prices for the meats because they vary depending on brand or type. I am also not including the prices of the dip ingredients because the recipes were used in previous articles.
As mentioned earlier, there are plenty of variants of the “bar” party. Basically, anything you just lay out for others to put together is a bar party. 
While it is still cold outside, I would highly recommend getting several pots or crockpots full of various hot chocolates: peppermint, regular, gingerbread, etc.
You could also make a nacho bar by starting with a bowl of chips and various dips. If you did this, you could use all of the hard shell tacos not eaten at the taco bar.
Then, there is the pasta bar. I made one of these last month and it might be my favorite variation. I made a couple different types of cooked pasta and had folks add sauces, veggies, meat and cheese.
Another easy option is to host a make-your-own-pizza pizza bar. Attendees can start with soft tortillas, mini pizzas like those in Lunchables or homemade cooked pizza doughs. From there, everyone can add their favorite toppings.
There are also healthier options, such as fruit bowls, smoothie bars or a DIY parfaits bar.
It goes without saying the idea applies to desserts, like the ice cream sundae bar.
The most important things with these bar party ideas are keeping it simple for you, and knowing your audience. Keep it simple by using only dishes to be thrown out or dishwasher and microwave safe. I usually buy a 30 pack of cheap paper plates and a 30-count pack of cutlery.
Most of the time, there will not be more than 10 people participating. So, you will have extra stuff for next time, and plenty of stuff for people who throw their stuff out or cannot keep track of the stuff they set down somewhere. Those are the easy things to save time and money.
Now, the hard lesson: knowing the audience. This is important, because otherwise, a lot of money might be wasted. To make it easier on yourself, try only inviting people you know well, and center your bar party around what you think your friends will like.
Keep in mind, whatever you buy, you will have leftovers. For instance, I am not a fan of sour cream, but still bought it for my taco bar party and sent the remaining sour cream home with one of the guests. Make sure whatever you buy, you will be able to use in other recipes, to eat or have someone else eat.
Whatever you do, do it confidently and comfortably. Nothing should be so much trouble you cannot enjoy it while it is happening. Do not go nuts with it. Just take it easy, and enjoy the process and the outcome.