In depth: Using the D&D Adventure System components in your 4E game.
The Dungeons and Dragons Adventure System Board Games, Castle Ravenloft and Wrath of Ashardalon, feature what is basically a very stripped down version of the D&D 4th Edition Core Ruleset. Gameplay mechanics allow a group of players to delve into a dungeon crawl scenario without needing a Dungeon Master to control monsters or spring traps. The games come with 40 unpainted D&D miniatures, numerous tokens, and tiles that serve as the play area, which are interlinkable; the dungeon builds itself as players explore it, and is never the same twice.
Tiles, monsters, treasure, and events are randomized through shuffled decks of cards.
In preparing for my 4e game's journey into Castle Ravenloft, I was able to adopt a lot of the mechanics from the board games for the dungeon. The last thing I wanted was another boring delve with preplanned encounters, and this worked surprisingly well.
I went through all the tiles for Ravenloft and Ashardalon and made a single stack, primarily consisting of tiles with doors and hallways. I left out a lot of the tiles that were full rooms. I found the Secret Stairway tile and put it in the stack about 20 tiles down. Once a character stepped on a tile, I would place any adjacent tiles in a way that made sense.
My players are currently fifth level, so I started scouring the Monster Vault and MM3 for beasties that would fit the general undead theme, between levels 3 and 7, and found several that worked. I pared down the list to about 15 or 20.
Then I opened up Magic Set Editor and got to work. This was the time-consuming part, but it was made easy by having the WotC D&D Compendium open. Copy and paste and a little formatting, and pretty soon I had a deck full of monsters.
I went through the Encounters decks for both Ravenloft and Ashardalon and started taking notes for some traps and events to spring on the heroes, and made individual cards for those as well.
I got into Adventurer's Vault 2 and picked out a dozen magic items to drop in, and made cards for those (I do that for all magic items found in-game, though), copy and pasting from the Compendium.
Treasure drops were random, based on d12 rolls, and the amount varied with the different creatures. I placed the number of rolls on the treasure chart as the monster's "casting cost" in the upper right corner. I made cards with the random charts on them to have right in front of me.
Print out the cards on decent cardstock paper, cut out and shuffle into a deck (leaving out the individual magic item cards, hand those out when they come up on a roll for treasure). Draw a card on every character's turn as they move through the dungeon. I admit I tended to skip the draw a few times if they were getting swamped, but as soon as they took out a couple monsters, I started drawing again.
You'll want to have figures or tokens set aside for all possible monsters to avoid bringing the game to a halt while you search for them. Other than that, using a little common sense while you implement the results of the card draws goes a long way. Spread the monsters out around the board if you can. And don't draw yourself into a corner with your tile placement!