OpenSSL uses PKCS#12 (what is this a format?) as input and PEM as output - http://www.openssl.org/docs/apps/pkcs12.html#COMMAND_OPTIONS
More discussion on formats - http://www.bo.infn.it/alice/introgrd/certmgr/node2.html
Converting between formats - http://support.sas.com/documentation/cdl/en/secref/62092/HTML/default/viewer.htm#a002815156.htm
See what is in a cert - http://www.sslshopper.com/certificate-decoder.html
Converting from Open SSL to IKeyman
Import OpenSSL to IKeyman - http://publib.boulder.ibm.com/infocenter/tivihelp/v2r1/index.jsp?topic=/com.ibm.itame.doc/ss7cumst46.htm
IBM IHS import experience - http://luskwater.blogspot.com/2009/04/importing-certificates-from-openssl.html
Import OpenSSL to IKeyman (this doc looks complete) - http://i-proving.ca/space/Brett+Dubroy/blog/2008-08-07_1