Are they worth investing in? do you think that any of them will soon be like bitcoins price?
I won't speak for PPC of NMC as I don't know enough about them, but I don't think it would hurt to diversify a bit and have 1%-5% of Cryptocurrency portfolio in LTC, especially if you can buy in ~ 0.022/BTC or less.
It's very much a higher-risk investment, but if/when it gets to MtGox (and assuming this happens before MtGox's volume declines too sharply as it has seemed to) there could potentially be a speculation bubble for it that happens independently of BTC's price. There's a lot of new speculation money that entered (and is entering) this market following March/April, and psychologically probably wish they had bought BTC when it was only $5.
I also think the specificity and scarcity of ASIC miners stands to affect the SHA/Scrypt relationship in an interesting way that will play out over the next few months - the sharp spike in difficulty coming tomorrow will really make huge waves.
