The situation is as follows:
You can immediately use any of the RPC adapters that you can find on the download section of this site, so these few coins are covered. You can connect to the following wallets: LTC, DOGE, FTC, GridCoin, GoldCoin. You can also easily modify the Litecoin adapter to connect to other coins based on the same technology. This requires that you maintain servers that run these wallets.
Alternatively you can use a cloud wallet which requires little to no maintenance. For maximum coin coverage, your best bet right now is to use the CoinPayments adapter instead. The adapter supports any coins that CoinPayments supports, so the list is dynamic. For a list of coins used by CoinPayments, refer to this list: https://www.coinpayments.net/supported-coins