It's part of the Oxford charity's coronavirus response appeal.
Sunglasses worn by Dame Helen and a signed tambourine belonging to former Oasis singer Gallagher have gone up for sale.
Cufflinks worn by Pegg to the UK premiere of Star Wars: The Force Awakens and a pair of singer Faith's are also under the hammer.
Pegg said: "You can't beat a set of Star Wars-related cufflinks worn by Unkar Plutt himself - especially ones that raise money for Oxfam - so get bidding to raise funds for people battling coronavirus around the world."
DJ Fatboy Slim has donated an amplifier, while Strictly Come Dancing professional Katya Jones has donated a silver sequined jumpsuit.
Fee Gilfeather, from Oxfam, said: "Generous donations like these generate vital funds for Oxfam's work fighting poverty and helping protect some of the world's poorest communities from coronavirus - at a time when the pandemic is making many people more vulnerable than ever.
"Many people have had a clear-out during lockdown and it's great that the celebrities and artists are donating these items to Oxfam with the benefit of raising money for our coronavirus appeal, as well as protecting the planet.
"Donating clothes to Oxfam gives garments a chance of a new life, instead of being destined to a landfill."
The online auction launched on Sunday and is open for a week.