The simplest rig I've used was:
Microphone (actually two), decent Audio Technica dynamic, not expensive.
My 1982 Technics cassette recorder, which has nice needle-type VU meters and stereo mic input jacks (try and find such a thing these days).
I press Record and knock out a tune.
(Here comes the tricky part.)
I got a cable from Radio Shack that has two RCA phono plugs on one end and a stereo 3.5 mm mini plug on the other.
The phono plugs go into the Line Out jacks of my cassette player.
The mini plug goes into the Line In on my PC.
It is possible to play your tape recording back through the PC but I just listen to the playback through the cassette deck's headphone jack.
Here's my next big secret. There are any number of sound capture apps to choose from, and there's probably one that came with your operating system.
I chose a shareware product called Sound Recorder by Polderbits out of the Netherlands.
http://www.polderbits.com/
It was cheap but it does a great job, and it is simple. That's s-i-m-p-l-e.
Start Sound Recorder.
Click it's Record icon.
Press Play on the cassette player.
Stop them after the song is over.
Save the file on the PC in the format you want (Usually mp3).
You now have a recording you can upload to Soundclick.com or whatever site you want to use. That process isn't much different than uploading photos.
I'm getting a little more complicated lately by experimenting with my mixers before sending it to the PC. I almost bought a mixer with a USB port to start doing this all directly to the PC and leave out the cassette part, but -- you know --- geezerness. For what I do, and what I need, my simple setup works alright. And if I need more than that I'll go to my friend's studio and let him do it professionally.
Hope that is of some value, and please feel free to ping me with any questions! There's gotta be a mountain of experience among the members here, too!
Good luck!
Guildmark