A wiki entry is a good idea, however I will give a brief overview below as a wiki entry will require the filling of several gaps. My conversion experience is limited to cassettes so I cannot help you with the floppy disk issue, I have will have to leave it to others to fill the gaps on converting cartridges and disks.
Converting Cassettes to CAS Files
Hardware Set Up
Connect the audio out or earphone socket of a cassette player to the aux. input or microphone socket of your computer.
Software
Use an audio recording program of your choice to create a wav file, mono with a sampling rate of ~22 kHz should suffice.
There are two methods available to convert the wav file to a cas file, the first is by using an emulator that accepts wav files (such as recent versions of XRoar), the second is by using conversion software.
Emulator Method using XRoar
This is most suited for BASIC and non-autostarting machine code programs neither of which are multi-part.
Start up XRoar and make sure that Dragon DOS is not running (if it is, either remove the Dragon DOS ROM from the relevant XRoar directory and restart XRoar, or press Control+E then Control+Shift+R). Press Control+L and select the wav file, then CLOAD/CLOADM as appropriate. After the program has loaded press Control+W, type in a file name (including the .cas extension), and CSAVE/CSAVEM (remember to use the same name that was displayed during loading) to create the cas file. CSAVEM takes the form of CSAVEM"filename",[start],[end],[entry]
where (I believe)
[start] = PRINT PEEK(487)*256 + PEEK(488)
[end] = PRINT PEEK(126)*256 + PEEK(127) - 1
[entry] = PRINT PEEK(157)*256 + PEEK(158)
(Note. This is why Dragon DOS must be disabled as these PEEKed addresses change when DOS is running.)
Conversion Software using DC
There are other conversion programs available but most of these programs strip out the leaders (periods of silence before the program header) to create smaller cas files - not a problem for older emulators, but a problem for those emulators that better emulate the Dragon's tape loading routine. If you have created a cas file with one of these conversion programs you will have to pass this cas file through FIXCAS before you can load it in the most current emulators. To avoid this extra work you should instead use the version of DC.EXE available for download from this site.
Unlike XRoar (emulator method), conversion programs are suitable for autostarting and multi-part programs, they also overcome the need to find out a machine code programs start, end, and entry addresses.
Before using DC bear in mind that it is a DOS program that must be used from the command line. Being a DOS program means that the program follows the DOS filename restrictions (up to eight characters, a full stop, then an extension of up the three characters), so first rename your wav file to comply with these restrictions. For example, you could rename Crazy_Painter.wav to C_Paint.wav. After conversion you can always rename the relevant files with longer filenames.
As an aside, if you often use the command line in MS Windows you may find the Microsoft Powertoy "Open Command Window Here" of great use. The XP version is available from here
http://www.microsoft.com/windowsxp/Down ... rtoys.mspx , other versions of Windows may have their own version (use a search engine to find the Powertoys page for your version of Windows, always use Powertoys designed for your version of Windows).
To use DC use the following construct:
DC filename.wav
The .wav extension is important. If all goes well DC will create a cas file, complete with a suitable name. More likely it will not go smoothly and you will be asked to enter values for wavelength and volume, it will take trial and error for each file to find values that work. Sometimes it may be easier to re-record the wav file, though one tip that I've found useful is to go back to the audio recording program, load the troublesome wav file, invert the wave form, and save the result, then use DC on the new wav file.
Conversion Software using Sixxie's XRoar-0.23pre3-tapemangle
Since I've only just downloaded it, it won't surprise you to learn that I have yet to use it. However on the face of it, it seems to overcome the problems of both DC and using the XRoar emulator approach.