Noteworthy roguelikes/dungeon crawlers to grab during the Summer Sale

my top 3:
Nethack
Angband
Moria

FTL is pretty fun.

risk of rain and FTL

The binding of isaac no doubt. ftl also good

Dungeon Crawlers
Might and Magic X of course
Paper Sorcerer is another nice cheap dungeon crawler

Roguelite
Delver is a first person dungeon crawler rougelite, not demanding or complex, just fun.

Roguelike
Desktop Dungeons
Dungeons of Dredmor.
Neo Scavanger is a greate roguelie that has not gotten the popularity it deserves. Seriously one of the best I've ever played.

Dungeons of dredmor is close to the oldschool roguelikes and not too hard to get into

Sword of the Stars: The Pit is $1.79 on Steam.

For an even better deal, the Gold Edition with 2 DLC packs is $1.79 on Amazon.

The binding of isaac will go on sale for like $1 im sure + the dlc for another $1 its great

By "old'school" I assume you mean turn-based? I haven't played many but here are some on my wish list:

Famaze,
Dungeon of the Endless,
Dungeonmans,
Quest of Dungeons.

If you don't mind real time rogue-likes then try:

Rogue Legacy,
Pixel Boy and the Ever Expanding Dungeon,
Legend of Dungeon.

And if you want really old-school try Fatal Labyrinth. Steam sells it alone or else as part of the Sega Genesis Classics Pack 2.

For dungeon crawlers, I'd recommend any of the Dungeon Siege, FATE, Torchlight, or TitanQuest games.

The Binding of Isaac, FTL, i recently got One Way Heroic, seems fun, but didn't tried it yet ($0.87)

Grimrock is the only option. :)

rougelike, it's pronounced rou-ge-like

Tales of Maj'Eyal seems to fit what your looking for perfectly.

Noteworthy dungeon crawlers:

Legend of Grimrock - I'm still playing through it, best modern Dungeon crawl atm. Nice for a beginner.

Dungeon Siege 3 can aslo be called a Dungeon crawler in some way, but there's more of an action rpg in it. Personally I love DS3 more than the first two games due to a rather solid plot and rather interesting characters. Fights can be pretty hard sometimes, but it's a nice start as well.

Dark Souls ONE and TWO games can also be considered a dungeon crawler in some way, but still it's more of a slasher in them. Extremely good games, not too hard to master, but you'll die a lot. Dying here is a way to learn the game. If you beat them - you can beat any game at all.

Severance: Blade of Darkness - same as Dark Souls (even better than Dark Souls in some way). Rather hard fighting system, still considered by many one of the best rpg-slashers of all time.

Arx Fatalis - old school never dies. Beaten it two or three years ago, still a wonderful game. Rather complex magic and quest system, you need to be good at RPG genre in general.

Rune Classic - another case of a slasher, but with a sense of dungeon crawl.

Wizardry series - came out recently on Steam, get a pack of 6,7,8 if you can. Very complex RPG and dialog system.

Might & magic series are classic dungeon crawlers, you can get them on GOG. True old-school, only for pure enthusiast, watch trailers first.

http://groupees.com/bagb7
Tallowmere looks great, but it's not finished yet. On the other hand, you can pink 4 games for 1$ and get desure/DRM free version, + steam key if greenlight. If you only want to play it, this is a great deal :)

• Desktop Dungeon - Kind of like minesweeper, but with monsters. Monsweeper! Note, there is a free alpha version.
• Recettear - Not the main aspect of the game, but it has a solid "inverse tower" dungeon. Personally I recommend getting the bundle if you don't have the other games.
• Rogue Legacy - Metroidvania Roguelike. Your deaths become a family tree. Demo.
• Hack Slash Loot - Pretty straight-forward Roguelike. Demo.
• Realm of the Mad God - Free, more of a shooter than a slasher, but it's definitely a crawler.
• Spiral Knights - If you can stomach the energy limitations and typical MMO shenanigans, go for it.

I can totally recommend Vulture for SLASH'EM or Nethack which is a graphical interface for them. So far I guess have spent hundreds hours on it. You can download it free on their website, but it is also on Greenlight. So everybody looking for an easier accessible Nethack should definetily give it a try!

Not on steam ( but free ) and not exactly a dungeon crawler ( but you can build a dungeon in fortress mode and then explore it in adventure mode ) but i'd still recommend the excellent Dwarf Fortress.