Mathematica supports many formats, with many subformats, variants and options.
"3DS" — 3D Studio format (.3ds)
"ACO" — Adobe color palette format (.aco)
"AIFF" — AIFF Macintosh sound format (.aif, .aiff)
"ApacheLog" — Apache access log file format
"AU" — 
law encoding Unix Audio Format (.au)
"AVI" — Microsoft AVI format (.avi)
"Base64" — Base64 ASCII encoding
"Bit" — sequence of binary bits
"BMP" — Microsoft bitmap format (.bmp)
"Byte" — sequence of 8-bit unsigned integers
"BYU" — BYU 3D geometry format (.byu)
"BZIP2" — bzip2 compression format (.bz2)
"CDED" — Canadian digital elevation data (.dem)
"CDF" — NASA common data format (.cdf)
"Character8" — sequence of 8-bit characters
"Character16" — sequence of 16-bit Unicode characters
"Complex64" — IEEE single-precision complex numbers
"Complex128" — IEEE double-precision complex numbers
"Complex256" — IEEE quad-precision complex numbers
"CSV" — comma-separated values (.csv)
"CUR" — Windows cursor resource format (.cur)
"DBF" — dBase database file (.dbf)
"DICOM" — DICOM medical image format (.dcm, .dic)
"DIF" — VisiCalc data interchange format (.dif)
"Directory" — filesystem directory hierarchy
"DXF" — AutoCAD 2D and 3D format (.dxf)
"EDF" — European Data Format (.edf)
"EMF" — Windows metafile and enhanced metafile formats
"EPS" — Encapsulated PostScript (.eps)
"ExpressionML" — Mathematica expression XML format (.xml)
"FASTA" — bioinformatics sequence format (.fasta, .fa, .fsa, .mpfa)
"FITS" — FITS astronomical data and image format (.fit, .fits)
"FLAC" — FLAC lossless audio codec (.flac)
"GIF" — static or animated GIF (.gif)
"Graph6" — dense graph format (.g6)
"GTOPO30" — USGS global topographic data (.dem)
"GZIP" — Unix gzip compression (.gz)
"HarwellBoeing" — Harwell-Boeing sparse matrix format
"HDF" — NCSA hierarchical data format (.hdf)
"HDF5" — NCSA HDF 5 hierarchical data format (.h5)
"HTML" — HTML format (.htm, .html), including embedded GIFs, CSS, etc.
"ICO" — Windows icon resource format (.ico)
"Integer8" — sequence of 8-bit signed integers
"Integer16" — sequence of 16-bit signed integers
"Integer24" — sequence of 24-bit signed integers
"Integer32" — sequence of 32-bit signed integers
"Integer64" — sequence of 64-bit signed integers
"Integer128" — sequence of 128-bit signed integers
"JPEG" — JPEG raster image format (.jpeg, .jpg)
"JPEG2000" — JPEG 2000/JP2 raster image format (.jp2, .j2k)
"JVX" — JavaView format (.jvx)
"LaTeX" — LATEX format (.latex)
"List" — numbers or strings, one per line
"LWO" — LightWave 3D file format (.lwo)
"MAT" — Matlab/Octave data format (.mat)
"MathML" — MathML math content format
"Maya" — Maya entity files (.ma)
"MBOX" — mbox Unix mailbox format (.mbox)
"MDB" — Microsoft Access database file (.mdb)
"MGF" — Wolfram
Mathematica MGF bitmap format (.mgf)
"MIDI" — MIDI music format (.mid)
"MOL" — MDL MOL molecular models and drawings format (.mol)
"MPS" — MPS linear programming system format (.mps)
"MTP" — Minitab portable worksheet format (.mtp)
"MTX" — Matrix Market sparse matrix format (.mtx)
"MX" — Mathematica serialized package format (.mx)
"NB" — Wolfram Notebook format (.nb)
"NetCDF" — Unidata scientific data format
"NOFF" — 3D object file format with normals (.noff, .cnoff)
"OBJ" — Wavefront OBJ format (.obj)
"ODS" — OpenDocument spreadsheet format (.ods)
"OFF" — 3D object file format (.off, .coff)
"Package" — Mathematica package source (.m)
"PBM" — ASCII portable bitmap format (.pbm)
"PCX" — Windows Paintbrush format (.pcx)
"PDB" — Protein Data Bank format (.pdb)
"PDF" — Adobe Acrobat PDF format (.pdf)
"PGM" — ASCII portable graymap format (.pgm)
"PICT" — Macintosh PICT format (.pict)
"PLY" — PLY 3D geometry format (.ply)
"PNG" — PNG raster image format (.png)
"PNM" — ASCII portable raster format (.pnm)
"POV" — POV-Ray ray-tracing object description format (.pov)
"PPM" — ASCII portable color pixmap format (.ppm)
"PXR" — Pixar raster format (.pxr)
"RawBitmap" — pure binary bitmap data
"Real32" — IEEE single-precision real numbers
"Real64" — IEEE double-precision real numbers
"Real128" — IEEE quad-precision real numbers
"RIB" — Renderman interchange format (.rib)
"RSS" — RSS feed format (.rss)
"RTF" — Microsoft Rich Text Format (.rtf)
"SCT" — Scitex CT prepress format (.sct)
"SDTS" — SDTS DLG and DEM spatial data files
"SND" — SND file format (.snd)
"Sparse6" — sparse graph format (.s6)
"STL" — stereolithography format (.stl)
"String" — arbitrary data as a
Mathematica string
"SVG" — Scalable Vector Graphics format (.svg)
"SWF" — Flash multimedia format (.swf)
"SXC" — OpenOffice 1.0 spreadsheet file (.sxc)
"Table" — arbitrary tabular data (.dat)
"TAR" — Unix tar archive (.tar)
"TerminatedString" — null-terminated string
"TeX" — TEX document format (.tex)
"Text" — plain text (.txt)
"TGA" — TrueVision Targa format (.tga)
"TIFF" — TIFF raster image format (.tiff, .tif)
"TSV" — tab-separated values (.tsv)
"UnsignedInteger8" — sequence of 8-bit unsigned integers
"UnsignedInteger16" — sequence of 16-bit unsigned integers
"UnsignedInteger24" — sequence of 24-bit unsigned integers
"UnsignedInteger32" — sequence of 32-bit unsigned integers
"UnsignedInteger64" — sequence of 64-bit unsigned integers
"UnsignedInteger128" — sequence of 128-bit unsigned integers
"USGSDEM" — USGS ASCII DEM digital elevation file (.dem)
"UUE" — Unix uuencode format (.uue, .enc)
"VCF" — vCard format (.vcf)
"VRML" — Virtual Reality Modeling Language format (.vrml)
"WAV" — Microsoft WAV audio format (.wav)
"Wave64" — Sony Wave64 audio format (.w64)
"WDX" — Wolfram data exchange format (.wdx)
"WMF" — Windows metafile format (.wmf)
"X3D" — X3D XML geometry format (.x3d)
"XBM" — X bitmap format (.xbm)
"XHTML" — XML-syntax HTML (.xhtml)
"XHTMLMathML" — XHTML with embedded MathML
"XLS" — Excel spreadsheet format (.xls)
"XML" — arbitrary XML (.xml)
"XPORT" — SAS interchange format (.stx, .xpt)
"XYZ" — XYZ molecule geometry file (.xyz)
"ZIP" — Windows ZIP archive (.zip)
"ZPR" — Z Corp 3D printer format (.zpr)
