Also known as "Borax" and has the chemical formula of Na₂B₄O₇.10H₂O, gives transparent crystals. Solubility: 27 g/L (anhydrous, 20°C, water).

Credit: picture by Luc Van Meervelt

Has the chemical formula of CuSO₄.5H₂O, gives blue crystals. Solubility: 390 g/L (anhydrous, 20°C, water).

Credit: picture by Luc Van Meervelt

Also know as "KDP", has the chemical formula of KH₂PO₄, gives transparent long crystals. Solubility: 22 g/100 mL (anhydrous, 25°C, water).

Credit: picture by Luc Van Meervelt

Has the chemical formula of (NH₄)2Mg(SO₄)₂.6H₂O, gives transparent long crystals. 

The crystallization is started from ammonium sulfate and magnesium sulfate. Dissolve at room temperature equivalent amounts of both salts in water (e.g. 0.4 mol of both compounds in 45-48 mL water). Stir until everything is dissolved. Now make the solution supersaturated by adding small amounts (2 to 5 gram) of both salts under gentle heating (max. 30-40 °C). Cover the beaker and allow to cool at room temperature. Now proceed with the crystal growth in the usual way.

Credit: picture by Luc Van Meervelt

Also know as "Seignette salt" or "Rochelle salt", has the chemical formula of KNaC₄H₄O₆.4H₂O, gives transparent long crystals. Solubility: 630 g/L (anhydrous, 20°C, water).

Credit: picture by Luc Van Meervelt

Also know as "Mohr's salt", has the chemical formula of (NH₄)₂Fe(SO₄)₂.6H₂O, gives light green crystals. Solubility: 269 g/L (20°C, water).

 
Credit: picture by Luc Van Meervelt

Also known as "Red Prussiate of Potash" and has the chemical formula of K₃Fe(CN)₆. The recipe below gives red monoclinic crystals. Solubility: 464 g/L (20°C, water). 

Dissolve 93 grams of potassium ferricyanide in 200 cc of warm water, cover the solution, and allow it to cool. 

Credit: picture by Wayne Schmidt (http://www.waynethisandthat.com/crystals.htm)

Chemical formula: Cu(CH₃COO)₂.H₂O. The recipe below gives blue-green monoclinic crystals. Solubility: 72 g/L (20°C, water). 

Dissolve 20 grams of copper acetate monohydrate in 200 cc of hot water. If a scum of undissolved material persists, add a few drops of acetic acid and stir well. Cover this solution, and allow it to cool and stand for a few days; usually it will deposit crystals spontaneously.

Credit: picture by Coba Poncho

Chemical Formula: CaCu(CH₃COO)₂.6H₂O. The recipe below gives blue, tetragonal crystals. 

Add 22.5 grams of powdered calcium oxide to 200 mL of water, pour into the mixture 48 grams of glacial acetic acid, and stir until the solution is clear. If there is a small insoluble residue, filter the solution. Dissolve separately 20 grams of copper acetate monohydrate in 150 cc of hot water. Mix the two solutions, cover the mixture, allow it to cool for a day. If it does not deposit crystals spontaneously, let a drop of the solution evaporate and scrape the resulting seeds into the bulk of the solution.

Sodium Chloride

Chemical Formula: NaCl. Also known as table salt. Solubility: 35.9 g/100 mL (20°C, water). 

NaCl tends to form smaller crystals, or less well formed crystals because the solubility barely changes at all as a function of temperature; at 20°C, one can dissolve 35.9g of NaCl in 100g of water, and at 100°C, just 39.2g per 100g of water. The most appropriate method of growing sodium chloride crystals is therefore by evaporation of a saturated solution. Small (sub-millimetre) clear cubes with smooth faces will grow on the bottom of your glass dish or jar, or on any thread suspended in the jar. Larger crystals tend to develop hopper faces, or even more erratic growth habits. One interesting experiment to try is to see how the growth morphology changes if you add small quantities of other substances - a smidge of copper sulfate perhaps, K-alum, or sodium nitrate - to your saturated salt solution.

Chemical Formula: C₁₂H₂₂O₁₁. Also known as saccharose or table sugar. Solubility: 211.5 g/100 mL (20°C, water). 

Cane sugar produces great crystals without too much trouble, provided you can be patient. Dissolve ~500 grams of sugar per 100 mL of hot water, and leave to cool. The pale silvery-yellow solution is very viscous when supersaturated, and can take from a week to over a month to start producing crystals, depending on how big a jar you're using. Crystals shoot from smaller volumes of liquid quite quickly and can grow to a length of a few millimeters. Use these as seeds to grow much larger crystals. You can grow very pretty single crystals over a period of just a few weeks. Sucrose is slightly deliquescent; in other words, the crystals 'sweat' a bit. You'll find the crystals become slightly moist and sticky, even when you've dried them, particularly in a warm room.

Credit: http://www.solarnavigator.net/solar_cola/sugar.htm

Chemical formula: KCr(SO₄)₂•12(H₂O). Also known as chromium alum. Gives deep purple crystals. You can grow a clear alum layer around the purple crystals.  

1. The growing solution will consist of a chromium alum solution mixed with an ordinary alum solution. Make a chromium alum solution by mixing 60 g of potassium chromium sulfate in 100 ml water.
2. In a separate container, prepare a saturated solution of ordinary alum by stirring alum into warm water until it will no longer dissolve.
3. Mix the two solutions in any proportion that you like. The more deeply colored solutions will produce darker crystals, but it will also be harder to monitor crystal growth.
4. Grow a seed crystal using this solution, then tie it to a string and suspend the crystal in the remaining mixture.
5. Loosely cover the container with a coffee filter or paper towel. At room temperature (~25°C), the crystal can be grown via slow evaporation for as little time as a few days or as long as a few months.
6. To grow a clear crystal over a colored core of this or any other colored alum, simply remove the crystal from the growing solution, allow it to dry, and then re-immerse it in a saturated solution of ordinary alum. Continue growth for as long as desired.

 
Credit: picture by Wayne Schmidt (http://www.waynethisandthat.com/crystals.htm)