Goodman Games has two modules that are only $2 on RPGNow. One is
Transmuter's Last Touch, which I think is a blast. The other is "The Dragonfiend Pact", which I purchased, but have not had time to read yet. I have read through other Goodman Games modules, and they tend to be of high quality and be creative adventures. They do indeed remind me of the old days.
If you're looking for a bunch of cheap adventures, the WoTC list mentioned above is your best bet. There are some good ones in there. (I really liked "The Ettin's Riddle", but it's not a typical dungeon crawl.)
For an inexpensive collection of adventures, there is also
Adventure 1 from Alderac Entertainment. This is a collection of 24 adventures. They're not all classic dungeon crawls, but there's plenty of material in there. Also, quite a few of them are short and couple be played in only a couple of your one-hour sessions.
In all fairness, I should warn that these adventures are not as high quality as the Goodman Games ones. They're not quite as well written, there are more errors, and there are some oddities in the book (like a missing magic item). However, for less than $1 per adventure, the only products I've found that beat them for value have been free ones.
That being said, I have run a couple of the adventures and prepared some others. They're generally easy, quick to read through, and fairly simple adventures. They also do not require any special prestige classes or extra books.
There is a second collection, called
Adventure 2 which is a similar collection of adventures. I have not purchased this one yet, so I do not know what it is like.
In grabbing URLs for the links above, I just noticed that
MonkeyGod Productions has all of their modules on sale for $1 each right now.
MonkeyGod Presents: Shadows Under Thessalaine is an excellent adventure. It takes some time to prepare because there are three distinctly different chapters, but I and my players had a blast with this one just recently. (I especially love the BBEG, but I can't say why without spoiling the module completely.) If you want to spend $1, I highly recommend this one.
If you want some really old school stuff, and don't mind having to convert everything, there are some boxed sets of old D&D modules that are scanned and for sale. You can get them on a couple of different web sites, including RPGNow. The prices seem to vary a bit and there are sales. I picked up a "Temple of Elemental Evil" set for about $4 that is about 150 pages long and has 16 pages or so just of maps. That would keep you in adventures for quite some time. There are also compilations or boxed sets of the drow and giants series.