I've done a little research, but my evidence is neither here nor there.
I found this device on amazon which supposedly lets you plug something usb into a 3.5mm jack. But from the comments of the product, it looks like people are having a hard time getting this working for their devices.
So if your microphone requires a lot of power to operate, this solution will not work as it will not supply adequate power. However, if your microphone is simple, and doesn't require a lot of power (for example, isn't too high quality and doesn't do too much processing inside it), it may work.
So my suggestion would be, if you are stuck and cannot find anything else to do, try using one of these cables and see if it does what you wanted, especially since they're only $5, and if it doesn't work, oh well, it was only $5.
They already do (one example shown)
Capacity: 30 GB.
Interfaces: High-speed USB 2.0, compatible USB 1.1, PC & Mac USB Host port compatible Mass Storage Device Built-in WiFi connection (802.11b technology) IRDA 115 kb/s port.
Operating system: Linux Qtopiaâ¢ with embedded ARCHOS multimedia applications.
Video playback: MPEG-4 SP with MP3 or ADPCM stereo sound, near DVD quality up to 704x480 @ 30 f/s (MTSC), 720x576 @ 25 f/s (PAL), AVI file format*.
Video recording: MPEG-4 SP with MP3 stereo sound, near SVCD quality (optimised resolution for standard TV through composite video line-in) with up to 512x384 @ 30 f/s, in AVI format*