Greetings, brethern
up to now, we do not have any official list for acts of heresy. Besides what common sense tells us (for example denouncing the god-emporer, holding back the planetary tithe). Since for some of us (those GMing a group from Ordo Hereticus) some examples might be handy. A while I go, I noticed that all the "Calixis most wanted" (DotdG) come with a short summary of their crimes. A summary entitled "Confirmed Heresies".
What follows are some conclusion for examples of Heresy, open to discussion. Feel free to enter further points you found out, put please only add those you can quote a DH, RT or DW source for. Thanks!
Atrocities against Mankind; based on Myrchella Sinderfell (DotdG; p233). Based on here, I assuem that any grand slaughter of humans that is not justified by a war against traitors or a just purging would count as heresy
Witchcraft: okay, that is an easy one. Just added for completeness (p.234; DotdG). Funny thing is: "torture and multiple counts of murder" are listed in the same columne. Which leads the source a little ad absurdum. If torture would be heresy, the Imperium would just have turned into a place moraly a little above our actual western civilization. If murder would be heresy, the Arbites would need to sullen there hands witch common crimes. Which is said they do not.
Mental Violation: (p.234 DotdG).A nice point, me thinks. This would forbid a psyker to read another man´s mind if he isn´t justified to do so (working for a court, the inquisiton, the arbites, the governours seret police). But how is a pysker to proof his innocence?
Wanton Destruction: (p.234 DotdG). Again, a point that seems very mundane. Perhaps a question of scale?
Piracy (p.234 DotDG)
Murder of a Witchunter:(p.234 DotDG) which I deem to be only the case for "sanctioned witchhunters". Those announced by the Ministorum and recognized by the Ordo Hereticus (see BoM for Witchhunters).
Destruction/Killing of a Planet: (p.235) which is something... obvious.
Corrupting of faith/a faithfull sect; Founding of a heretical sect: (p.234) which seems to refer to "classical heresy", spreading of a heretical teaching among the faithful
Inciting Rebellion: (p.235) again, an obivous one.
Betrayal of the Holy Ordos / Killing of his agents (p.236) which makes inter-Inquisitional warfare a really dirty deed
Killing of members of the Adepta: This is an extrapolation of the mentioned killing of an Arbites Team (p.236). My reason behind this interpretion is that it was heresy because they were direct servants of one of the Adepta, which are in turn direct servants to Terra. Under this interpretion, every murder of a member of one of the Adepta would be reason for an investigation of the Arbitrators and/or the Inquisition.
The fact that the destruction of a Member of the Mechanicus is listed on p.237 DotdG supports me in my opinion
Desecration & Tomb robbery: (p.237 DotdG). Desecration is no surprise, but tomb robbery seems to be playing in the same league. Perhaps a proper grave is something sacral?
Possesion of Forbidden Lore; Necromancy (p.237 DotdG) the first one is no surprise, the second is not either. But why is it listed seperately? Perhaps it is even more foul then witchcraft? Or perhaps the FFG authors only wanted to ensure to bring about the point what Magos Vathek (the accused Heretek) is about?
Multiple Accounts of Murder; Cannibalism; (p.238 DotdG) Again, the mentioning of murder surprises me. This might be a misunderstanding on part of the author (to what is Heresy or what is mere crime). Otherwise, the Arbites will be really busy in the grim-dark world of 40K. Cannibalism is a nice point here. Especially if one takes "corpse starch rations" into account. My conclusion is that the imperial definition for cannibalism is the killing of a human with the intention of consumption. So recycling the dead is not sinful as long as they were not killed for just this reason (alone).
Slaving (p.238 DotdG) again, a little surprise. But on the other hand, perhaps that is the reason why you never here "slavery" in the DH-fluff but only "contract slavery" (holding a worker under a contract which rules ensure that he will never ever be able to repay his oder her depts).
Gerrymandering: (p.238 DotdG): my english is not good enough for this. What is the meaning?
Fraud, Blackmail (p.238 DotdG): this points are to me proof that even official DH sources are to be taken with a grain of salt. Either this, or the Arbitrator or busy with a lot of things.
Impersonation of an official of an Adepta: (p.238 DotdG) I tend to except this a heresy and not as an example of the above since it puts the Adepta into a special place withini the Imperium.
Illegal Sale of Holy relics: (p.238 DotdG) This raises the question: under which circumstances is a sale of holy relics legal? What makes it illegal? Does the Ministorum have to be asked for permission? Is it illegal to buy from other sources but the clerics of the Ministorum?

I think that it is only heresy in space. This is based on the assumption that the void lanes are vital for the survival of the Imperium of mankind and thereby a direct act against the will of the god-emperor.
(yep, it is wobbly. But somehow feels right).
Since the source seems to establish that murder/impersonation of members of the Adepta are not only crime but heresy, it would be the logical conclusion that other crimes against them (as the mentioned) are heresy as well!