I've been recording and posting my classes online for students to review and use ever since David Williams taught me this trick. Here's the best way I have found to do it.
I use the built-in Voice Memos app on the iPhone (or an iPod touch would do too).
(I did try the AudioMemos app, but I found it confusing to use and the sound quality not as good, unless you let it record WAV files, and then you have a 400+MB file.)
Here's the fancy bit: I stick it in my shirt breast pocket, upside down, so that the mic is facing up towards my face. Surprisingly, it works pretty well. Wearing a jacket muffles things a bit, as does setting the iOS device down, or carrying it around. I find using the breast pocket does a nice job. This doesn't record student questions or comments very well, of course, but nothing would without microphoning everyone, which is impossible.
The next step is to get the recordings off your phone and onto your computer. You can let iTunes transfer and sync your recordings, but I found that I ended up with bad data filling up my iPhone (the nefarious Other category); old voice memos would creep back onto my phone somehow. I ended up buying the PhoneView Mac app to try and fix the data corruptions on my iPhone. Sadly, PhoneView didn't solve the problem, and I had to restore the iPhone (this is very tedious, and not recommended).
But what PhoneView does do quite well is provide a way to pull your voice memos off your iPhone without using iTunes. This is now how I get to my class recordings without invoking iTunes and leading to further data corruptions. I have Voice Memos set not to sync with iTunes.
At the end of the week I use Sound Studio on my Mac to edit the recordings. (You can use Audacity or GarageBand, but Sound Studio is the easiest in my book.) Using Sound Studio, I reduce the sample rate sound quality from the standard 44,100 down to 11,025. I find this gives a nice balance of sound quality and file size. The point here is to make the voice recording a manageable and downloadable size.
I also use Sound Studio to check the beginning and end of the recording. Sometimes there's dead space at the beginning, or I'm interrupted and don't start class exactly as the recording starts. Similarly, at times I forget to turn off the recording after class, which is quite dangerous if you're having a confidential conversation with a student! So I want to check to make sure the beginning and ending of the sound file is the proper beginning and ending of the class. Then I save the file, which is now about 10 MB for a 50 minute class.
The next stage is renaming the file. I found the best way of naming these files is as the class code, so PHIL 205, followed by a dash and the week number. I find it easiest to label my lecture notes and these podcasts with the week number as it standardizes my notes, whether it's a Monday-Wednesday-Friday class or Tuesday-Thursday class. I then attach a period and a number for which day it is., along with a rough title for that particular class session. So the Wednesday class in the third week of the semester would be PHIL 203-3.2 Kant and Ethics.
Finally, the last step is to upload the files. I have used a shared Evernote folder in the past, and I have also used Blackboard, and I'm ambivalent about which is better. One word of advice is to upload your files from campus, as the upload speeds at your institution will be wildly better than your home connection. After uploading the files, I change their label color to green, which invokes the Hazel rule I have to squirrel the recordings away on my hard drive. (If I should need an alternate assignment for a future class, these recordings could be quite useful.)
I like recording classes because it puts the emphasis where it should be, which is on the class experience and class time. It also means that students don't have to try and transcribe the class completely, but can listen to the class afterwards. It has been helpful for me to listen to the class afterwards as well!