The main thing a this age imo is to make it fun. I don't mean disguising the learning, but teaching them that learning IS fun. Most children of this age have good memories - both of mine could sing the alphabet song and recognise all their letters and numbers. That in itself doesn't mean they will read earlier - it is jut the same as learning all the trains of Sodor - but it means they are comfortable when they 'meet' letters later on.
Count everything - stairs, forks, socks etc. Chat about numbers - 'we need to get the bus with a 2 and a 1, can you see it? Oh look, there it is, 2 and 1!''how many plates do we need? Me, you and daddy, that's 1,2,3, ok, lets count the plates, 1,2,3'
Alphablocks, numtums, numberjacks, letterland, jolly phoncs :-)
Lots of 'exploring' - so let her get muddy, draw, bake and so on. 'Oh, what a lovely green painting, can you show me the red paint, brilliant! What colour is that? Yellow, lovely, I'm going to paint a lovly yellow triangle!'
Chat to her ALL the time, and not just in baby words. Listen to what she says and reply with respect.
Read read read. Join the library if you haven't already.
Nursery rhymes, poetry, songs, rhymes, picture books, chapter books, magazines, comics, signs and all sorts :-)
Don't let people hold you back (I got sick of that very quickly) but try to develop a chilled attitude - quite often you think they will never grasp something, but let them wander off and come back, do short bursts, nd eventually they can learn anything :-). The most important thing is to keep 'school' as a fun game, and remember that even when you aren't doing formal stuff she is always learning.