In reading the Chamber of Secrets, Neville worries he's going to be attacked by Slytherin's monster. He says, "Everybody knows I'm basically a Squib." But Neville can perform some magic, even if he's not good at it yet. So I'm wondering if Squibs can preform a little magic. I know they can see Dementors but can they produce any magic at all? Why would Neville think he's almost a Squib if he can do some magic.
Per Pottermore's Everything you need to know about Squibs
Although like a Muggle they can’t perform magic.
Which chimes nicely with Ron's description in Harry Potter and the Chamber of Secrets.
"A Squib is someone who was born into a wizarding family but hasn’t got any magic powers."
and JKR's article on squibs from her original website
A Squib is almost the opposite of a Muggle-born wizard: he or she is a non-magical person born to at least one magical parent. Squibs are rare; magic is a dominant and resilient gene.
A squib who can do some magic is therefore, by definition, not a squib, just a crap wizard.
No, they can't do any magic. Reason why Neville said he is almost a squib is that he was highly underestimating himself, plus he had his father's wand which wasn't completely loyal to him - he wasn't able of great magic with that. He turned out to be very gifted wizard later.