Lee Oskar is still the best reasonably-priced brand about, in my opinion. At £19.99 each, they are at the high end, but still worth owning at least a couple. A tip: get hold of a Lee Oskar Natural Minor harp, they're made with an excellent minor key noteset.
The only disadvantage I've had with Lee Oskar harps is that they feel a bit flimsy at first. Trust me, they're not, and you'll get used to it VERY quickly.
Other ones to look out for? Hohner's Big River series. £11.99 each, so they're a lot cheaper. But they only have the usual major diatonic keys available, and it's a lot harder to bend notes with them. Don't be tempted by the £16.99 Hohner Blues Harp series, which is designed to be an upgrade of the Big River. They may sound slightly better, but they're much tougher to play, they feel awful in the mouth, and you can't bend notes as easily with them. It's not worth it.
So yeah. Lee Oskar or Hohner Big River. Either's good. Plus for novelty value there's always the £4.99 fully-functioning Hohner Little Lady
*looks at his minature 4-hole Little Lady that's connected onto his keyring*...
As for what scale to buy, I'd recommend major keys in D, A, E or B. D and A would be the first to buy, but it really depends if you're going to be playing them as accompaniment to other music or if you're going to use them on your own.
Also, check out the Lee Oskar Natural Minor series, as I mentioned before. I have one in Eflatminor, but I wouldn't recommend that as I needed it to accompany a certain piece. But they're great (probably better) on their own than with accompaniment. Which keys to choose? Go for one in C or G.
Then there are the other Lee Oskar notesets - the Melody Maker and the Harmonic Minor. I have a Melody Maker in C and it's not a great noteset, I wouldn't recommend it. I don't have a Harmonic Minor harp, so I don't know, but looking at the notes I don't think it'll be that great. I dunno, I may have to get one to find out. Whatever, a Lee Oskar is still a Lee Oskar
What models are your harmonicas at the moment?