Can Catholics receive any of the sacraments via Skype?
Yes, you could conceivably be married by proxy, via Skype.
There can be no online confession:
Can. 964 §1. The proper place to hear sacramental confessions is a church or oratory.
§3. Confessions are not to be heard outside a confessional without a just cause.
See the Substantive Norms art. 4, which forbids the recording "by whatever technical means" of what is said in confession:
§ 2. With due regard for § 1, n. 5, also reserved to the Congregation for the Doctrine of the Faith is the more grave delict which consists in the recording, by whatever technical means, or in the malicious diffusion through communications media, of what is said in sacramental confession, whether true or false, by the confessor or the penitent. Anyone who commits such a delict is to punished according to the gravity of the crime, not excluding, if he be a cleric, dismissal or deposition.
All the other sacraments must be done in person because they require a physical matter:
- holy water for Baptism
- holy oil for Confirmation, Orders, and Extreme Unction (Last Rites)
- wheat bread for the Eucharist
- imposition of hands (+ investiture of the new Priests) in Holy Orders