How about operating systems?
Some operating system distributions that have shipped with potentially vulnerable OpenSSL version:
Debian Wheezy (stable), OpenSSL 1.0.1e-2+deb7u4
Ubuntu 12.04.4 LTS, OpenSSL 1.0.1-4ubuntu5.11
CentOS 6.5, OpenSSL 1.0.1e-15
Fedora 18, OpenSSL 1.0.1e-4
OpenBSD 5.3 (OpenSSL 1.0.1c 10 May 2012) and 5.4 (OpenSSL 1.0.1c 10 May 2012)
FreeBSD 10.0 - OpenSSL 1.0.1e 11 Feb 2013
NetBSD 5.0.2 (OpenSSL 1.0.1e)
OpenSUSE 12.2 (OpenSSL 1.0.1c)
Operating system distribution with versions that are not vulnerable:
Debian Squeeze (oldstable), OpenSSL 0.9.8o-4squeeze14
SUSE Linux Enterprise Server
FreeBSD 8.4 - OpenSSL 0.9.8y 5 Feb 2013
FreeBSD 9.2 - OpenSSL 0.9.8y 5 Feb 2013
FreeBSD Ports - OpenSSL 1.0.1g (At 7 Apr 21:46:40 2014 UTC)
How can OpenSSL be fixed?
Even though the actual code fix may appear trivial, OpenSSL team is the expert in fixing it properly so latest fixed version 1.0.1g or newer should be used. If this is not possible software developers can recompile OpenSSL with the handshake removed from the code by compile time option -DOPENSSL_NO_HEARTBEATS.
Should heartbeat be removed to aid in detection of vulnerable services?
Recovery from this bug could benefit if the new version of the OpenSSL would both fix the bug and disable heartbeat temporarily until some future version. It appears that majority if not almost all TLS implementations that respond to the heartbeat request today are vulnerable versions of OpenSSL. If only vulnerable versions of OpenSSL would continue to respond to the heartbeat for next few months then large scale coordinated response to reach owners of vulnerable services would become more feasible.